# Patent

## Title
Cluster computing support for application programs

## Abstract

A computer cluster system comprising a plurality of nodes and a software package comprising a user interface and a kernel for interpreting program code instructions is provided. In one embodiment, a cluster node module is configured to communicate with the kernel and other cluster node modules. The cluster node module accepts instructions from the user interface and interprets at least some of the instructions such that several cluster node modules in communication with one another and with a kernel can act as a computer cluster.

## Background
PRIORITY INFORMATION
This application claims priority to U.S. Provisional Patent Application No. 60/813,738, filed Jun. 13, 2006 and U.S. Provisional Patent Application No. 60/850,908, filed Oct. 11, 2006. The entirety of each of the above-referenced applications is hereby incorporated by reference and made part of this specification.


BACKGROUND
1. Field of the Disclosure
The present disclosure relates to the field of cluster computing generally and to systems and methods for adding cluster computing functionality to a computer program, in particular.
2. Description of the Related Art
Computer clusters include a group of two or more computers, microprocessors, and/or processor cores (“nodes”) that intercommunicate so that the nodes can accomplish a task as though they were a single computer. Many computer application programs are not currently designed to benefit from advantages that computer clusters can offer, even though they may be running on a group of nodes that could act as a cluster. Some computer programs can run on only a single node because, for example, they are coded to perform tasks serially or because they are designed to recognize or send instructions to only a single node.
Some application programs include an interpreter that executes instructions provided to the program by a user, a script, or another source. Such an interpreter is sometimes called a “kernel” because, for example, the interpreter can manage at least some hardware resources of a computer system and/or can manage communications between those resources and software (for example, the provided instructions, which can include a high-level programming language). Some software programs include a kernel that is designed to communicate with a single node. An example of a software package that includes a kernel that is designed to communicate with a single node is Mathematica® from Wolfram Research, Inc. (“Mathematica”). Mathematics software packages from other vendors and other types of software can also include such a kernel.
A product known as gridMathematica, also from Wolfram Research, Inc., gives Mathematica the capability to perform a form of grid computing known as “distributed computing.” Grid computers include a plurality of nodes that generally do not communicate with one another as peers. Distributed computing can be optimized for workloads that consist of many independent jobs or packets of work, which do not need to share data between the jobs during the computational process. Grid computers include at least one node known as a master node that manages a plurality of slave nodes or computational nodes. In gridMathematica, each of a plurality of kernels runs on a single node. One kernel is designated the master kernel, which handles all input, output, and scheduling of the other kernels (the computational kernels or slave kernels). Computational kernels receive commands and data only from the node running the master kernel. Each computational kernel performs its work independently of the other computational kernels and intermediate results of one job do not affect other jobs in progress on other nodes.
SUMMARY
Embodiments described herein have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of the invention as expressed by the claims, some of the advantageous features will now be discussed briefly.
Some embodiments described herein provide techniques for conveniently adding cluster computing functionality to a computer application. In one embodiment, a user of a software package may be able to achieve higher performance and/or higher availability from the software package by enabling the software to benefit from a plurality of nodes in a cluster. One embodiment allows a user to create applications, using a high-level language such as Mathematica, that are able to run on a computer cluster having supercomputer-like performance. One embodiment provides access to such high-performance computing through a Mathematica Front End, a command line interface, one or more high-level commands, or a programming language such as C or FORTRAN.
One embodiment adapts a software module designed to run on a single node, such as, for example, the Mathematica kernel, to support cluster computing, even when the software module is not designed to provide such support. One embodiment provides parallelization for an application program, even if no access to the program's source code is available. One embodiment adds and supports Message Passing Interface (“MPI”) calls directly from within a user interface, such as, for example, the Mathematica programming environment. In one embodiment, MPI calls are added to or made available from an interactive programming environment, such as the Mathematica Front End.
One embodiment provides a computer cluster including a first processor, a second processor, and a third processor. The cluster includes at least one computer-readable medium in communication at least one of the first processor, the second processor, or the third processor. A first kernel resides in the at least one computer-readable medium and is configured to translate commands into code for execution on the first processor. A first cluster node module resides in the at least one computer-readable medium. The first cluster node module is configured to send commands to the first kernel and receives commands from a user interface. A second kernel resides in the at least one computer-readable medium. The second kernel is configured to translate commands into code for execution on the second processor. A second cluster node module resides in the at least one computer-readable medium. The second cluster node module is configured to send commands to the second kernel and communicates with the first cluster node module. A third kernel resides in the at least one computer-readable medium. The third kernel is configured to translate commands into code for execution on the third processor. A third cluster node module resides in the at least one computer-readable medium. The third cluster node module is configured to send commands to the third kernel and configured to communicate with the first cluster node module and the second cluster node module. The first cluster node module comprises a data structure in which messages originating from the second and third cluster node modules are stored.
Another embodiment provides a computer cluster that includes a plurality of nodes and a software package including a user interface and a single-node kernel for interpreting program code instructions. A cluster node module is configured to communicate with the single-node kernel and other cluster node modules. The cluster node module accepts instructions from the user interface and interprets at least some of the instructions such that several cluster node modules in communication with one another act as a cluster. The cluster node module appears as a single-node kernel to the user interface. In one embodiment, the single-node kernel includes a Mathematical kernel. In some embodiments, the user interface can include at least one of a Mathematica front end or a command line. In some embodiments, the cluster node module includes a toolkit including library calls that implement at least a portion of MPI calls. In some embodiments, the cluster node module includes a toolkit including high-level cluster computing commands. In one embodiment, the cluster system can include a plurality of Macintosh® computers (“Macs”), Windows®-based personal computers (“PCs”), and/or Unix/Linux-based workstations.
A further embodiment provides a computer cluster including a plurality of nodes. Each node is configured to access a computer-readable medium comprising program code for a user interface and program code for a single-node kernel module configured to interpret user instructions. The cluster includes a plurality of cluster node modules. Each cluster node module is configured to communicate with a single-node kernel and with one or more other cluster node modules, to accept instructions from the user interface, and to interpret at least some of the user instructions such that the plurality of cluster node modules communicate with one another in order to act as a cluster. A communications network connects the nodes. One of the plurality of cluster node modules returns a result to the user interface.
Another embodiment provides a method of evaluating a command on a computer cluster. A command from at least one of a user interface or a script is communicated to one or more cluster node modules within the computer cluster. Each of the one or more cluster node modules communicates a message based on the command to a respective kernel module associated with the cluster node module. Each of the one or more cluster node modules receives a result from the respective kernel module associated with the cluster node module. At least one of the one or more cluster node modules responds to messages from other cluster node modules.
Another embodiment provides a computing system for executing Mathematica code on multiple nodes. The computing system includes a first node module in communication with a first Mathematica kernel executing on a first node, a second node module in communication with a second Mathematica kernel executing on a second node, and a third node module in communication with a third Mathematica kernel executing on a third node. The first node module, the second node module, and the third node module are configured to communicate with one another using a peer-to-peer architecture. In some embodiments, each of the first node module, the second node module, and third node module includes a data structure for maintaining messages originating from other node modules and a data structure for maintaining data specifying a location to which an message is expected to be received and an identifier for a node from which the message is expected to be sent.



BRIEF DESCRIPTION OF THE DRAWINGS
A general architecture that implements the various features are described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments and not to limit the scope of the disclosure. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements.
FIG. 1 is a block diagram of one embodiment of a computer cluster.
FIG. 2 is a block diagram showing relationships between software modules running on one embodiment of a computer cluster.
FIG. 3 is a block diagram of one embodiment of a cluster node module.
FIG. 4 is a flow chart showing one embodiment of a cluster initialization process.
FIG. 5 is a flow chart showing one embodiment of the operation of a cluster node module.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
For purposes of illustration, some embodiments are described herein in the context of cluster computing with Mathematica software. The present disclosure is not limited to a single software program; the systems and methods can be used with other application software such as, for example, Maple®, MATLAB®, MathCAD®, Apple Shake®, Apple® Compressor, IDL®, other applications employing an interpreter or a kernel, Microsoft Excel®, Adobe After Effects®, Adobe Premiere®, Adobe Photoshop®, Apple Final Cut Pro®, and Apple iMovie®. Some figures and/or descriptions, however, relate to embodiments of computer clusters running Mathematica. The system can include a variety of uses, including but not limited to students, educators, scientists, engineers, mathematicians, researchers, and technicians. It is also recognized that in other embodiments, the systems and methods can be implemented as a single module and/or implemented in conjunction with a variety of other modules. Moreover, the specific implementations described herein are set forth in order to illustrate, and not to limit, the disclosure.
I. Overview
The cluster computing system described herein generally includes one or more computer systems connected to one another via a communications network or networks. The communications network can include one or more of a local area network (“LAN”), a wide area network (“WAN”), an intranet, the Internet, etc. In one embodiment, a computer system comprises one or more processors such as, for example, a microprocessor that can include one or more processing cores (“nodes”). The term “node” refers to a processing unit or subunit that is capable of single-threaded execution of code. The processors can be connected to one or more memory devices such as, for example, random access memory (“RAM”), and/or one or more optional storage devices such as, for example, a hard disk. Communications among the processors and such other devices may occur, for example, via one or more local buses of a computer system or via a LAN, a WAN, a storage area network (“SAN”), and/or any other communications network capable of carrying signals among computer system components. In one embodiment, one or more software modules such as kernels, run on nodes within the interconnected computer systems. In one embodiment, the kernels are designed to run on only a single node. In one embodiment, cluster node modules communicate with the kernels and with each other in order to implement cluster computing functionality.
FIG. 1 is a block diagram of one embodiment of a computer cluster 100 wherein computer systems 110, 120, 130 communicate with one another via a communications network 102. Network 102 includes one or more of a LAN, a WAN, a wireless network, an intranet, or the Internet. In one embodiment of the computer cluster, computer system 110 includes processors 112a, 112b, memory 114, and optional storage 116. Other computer systems 120, 130 can include similar devices, which generally communicate with one another within a computer system over a local communications architecture such as a local bus (not shown). A computer system can include one or more processors, and each processor can contain one or more processor cores that are capable of single-threaded execution. Processor cores are generally independent microprocessors, but more than one can be included in a single chip package. Software code designed for single-threaded execution can generally run on one processor core at a time. For example, single-threaded software code typically does not benefit from multiple processor cores in a computer system.
FIG. 2 is a block diagram showing relationships among software modules running on one embodiment of a computer cluster 100. In the embodiment shown in FIG. 2, the kernel modules 206a-e are designed for single-threaded execution. For example, if each of the processors 112a, 112b, 122a, 122b, 132 shown in FIG. 1 includes only one processor core, two kernel modules (for example, kernel modules 206a, 206b) loaded into the memory 114 of computer system 110 could exploit at least some of the processing bandwidth of the two processors 112a, 112b. Similarly, two kernel modules 206c, 206d loaded into the memory 124 of computer system 120 could exploit at least some of the processing bandwidth of the two processors 122a, 122b. Likewise, the bandwidth of processor 132 of computer system 130 could be utilized by a single instance of a cluster node module 204e loaded into the computer system's memory 134.
In the embodiment shown in FIG. 2, each of the kernel modules 206a-e is in communication with a single cluster node module 204a-e, respectively. For example, the kernel module 206a is in communication with the cluster node module 204a, the kernel module 206b is in communication with the cluster node module 206b, and so forth. In one embodiment, one instance of a cluster node module 204a-e is loaded into a computer system's memory 114, 124, 134 for every instance of a kernel module 206a-e running on the system. As shown in FIG. 2, each of the cluster node modules 204a-e is in communication with each of the other cluster node modules 204a-e. For example, one cluster node module 204a is in communication with all of the other cluster node modules 204b-e. A cluster node module 204a may communicate with another cluster node module 204b via a local bus (not shown) when, for example, both cluster node modules 204a-b execute on processors 112a, 112b within the same computer system 110. A cluster node module 204a may also communicate with another cluster node module 204c over a communications network 102 when, for example, the cluster node modules 204a, c execute on processors 112a, 122a within different computer systems 110, 120.
As shown in FIG. 2, an optional user interface module 202 such as, for example, a Mathematica front end and/or a command line interface, can connect to a cluster node module 204a. The user interface module can run on the same computer system 110 and/or the same microprocessor 112a on which the cluster node module 204a runs. The cluster node modules 204a-e provide MPI calls and/or advanced cluster functions that implement cluster computing capability for the single-threaded kernel modules. The cluster node modules 204a-e are configured to look and behave like a kernel module 206a from the perspective of the user interface module 202. Similarly, the cluster node modules 204a-e are configured to look and behave like a user interface module 202 from the perspective of a kernel module 206a. The first cluster node module 204a is in communication with one or more other cluster node modules 204b, 204c, and so forth, each of which provides a set of MPI calls and/or advanced cluster commands. In one embodiment, MPI may be used to send messages between nodes in a computer cluster.
Communications can occur between any two or more cluster node modules (for example, between a cluster node module 204a and another cluster node module 204c) and not just between “adjacent” kernels. Each of the cluster node modules 204a-e is in communication with respective kernel modules 206a-e. Thus, the cluster node module 204a communicates with the kernel module 206a. MPI calls and advanced cluster commands are used to parallelize program code received from an optional user interface module 208 and distribute tasks among the kernel modules 206a-e. The cluster node modules 204a-e provide communications among kernel modules 206a-e while the tasks are executing. Results of evaluations performed by kernel modules 206a-e are communicated back to the first cluster node module 204a via the cluster node modules 204a-e, which communicates them to the user interface module 208.
Intercommunication among kernel modules 206a-e during thread execution, which is made possible by cluster node modules 204a-e, provides advantages for addressing various types of mathematic and scientific problems, for example. Intercommunication provided by cluster computing permits exchange of information between nodes during the course of a parallel computation. Embodiments of the present disclosure provide such intercommunication for software programs such as Mathematica, while grid computing solutions can implement communication between only one master node and many slave nodes. Grid computing does not provide for communication between slave nodes during thread execution.
For purposes of providing an overview of some embodiments, certain aspects, advantages, benefits, and novel features of the invention are described herein. It is to be understood that not necessarily all such advantages or benefits can be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention can be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages or benefits as can be taught or suggested herein.
II. Computer Cluster 100
As shown in FIG. 1, one embodiment of a cluster system 100 includes computer systems 110, 120, 13.0 in communication with one another via a communications network 102. A first computer system 110 can include one or more processors 112a-b, a memory device 114, and an optional storage device 116. Similarly, a second computer system 120 can include one or more processors 122a-b, a memory device 124, and an optional storage device 126. Likewise, a third computer system 130 can include one or more processors 132, a memory device 134, and an optional storage device 136. Each of the computer systems 110, 120, 130 includes a network interface (not shown) for connecting to a communications network 102, which can include one or more of a LAN, a WAN, an intranet, a wireless network, and/or the Internet.
A. Computer System 110
In one embodiment, a first computer system 110 communicates with other computer systems 120, 130 via a network 102 as part of a computer cluster 100. In one embodiment, the computer system 110 is a personal computer, a workstation, a server, or a blade including one or more processors 112a-b, a memory device 114, an optional storage device 116, as well as a network interface module (not shown) for communications with the network 102.
1. Processors 112a-b 
In one embodiment, the computer system 110 includes one or more processors 112a-b. The processors 112a-b can be one or more general purpose single-core or multi-core microprocessors such as, for example, a Pentium® processor, a Pentium® II processor, a Pentium® Pro processor, a Pentium® III processor, Pentium® 4 processor, a Core Duo® processor, a Core 2 Duo® processor, a Xeon® processor, an Itanium® processor, a Pentium® M processor, an x86 processor, an Athlon® processor, an 8051 processor, a MIPS® processor, a PowerPC® processor, an ALPHA® processor, etc. In addition, one or more of the processors 112a-b can be a special purpose microprocessor such as a digital signal processor. The total number of processing cores (for example, processing units capable of single-threaded execution) within all processors 112a-b in the computer system 110 corresponds to the number of nodes available in the computer system 110. For example, if the processors 112a-b were each Core 2 Duo® processors having two processing cores, computer system 110 would have four nodes in all. Each node can run one or more instances of a program module, such as a single-threaded kernel module.
2. Network Interface Module
The computer system 110 can also include a network interface module (not shown) that facilitates communication between the computer system 110 and other computer systems 120, 130 via the communications network 102.
The network interface module can use a variety of network protocols. In one embodiment, the network interface module includes TCP/IP. However, it is to be appreciated that other types of network communication protocols such as, for example, Point-to-Point Protocol (“PPP”), Server Message Block (“SMB”), Serial Line Internet Protocol (“SLIP”), tunneling PPP, AppleTalk, etc., may also be used.
3. Memory 114 and Storage 116
The computer system 110 can include memory 114. Memory 114 can include, for example, processor cache memory (such as processor core-specific or cache memory shared by multiple processor cores), dynamic random-access memory (“DRAM”), static random-access memory (“SRAM”), or any other type of memory device capable of storing computer data, instructions, or program code. The computer system 110 can also include optional storage 116. Storage 116 can include, for example, one or more hard disk drives, floppy disks, flash memory, magnetic storage media, CD-ROMs, DVDs, optical storage media, or any other type of storage device capable of storing computer data, instructions, and program code.
4. Computer System 110 Information
The computer system 110 may be used in connection with various operating systems such as: Microsoft® Windows® 3.X, Windows 95®, Windows 98®, Windows NT®, Windows 2000®, Windows XP®, Windows CE®, Palm Pilot OS, OS/2, Apple® MacOS®, MacOS X®, MacOS X Server®, Disk Operating System (DOS), UNIX, Linux®, VxWorks, or IBM® OS/2®, Sun OS, Solaris OS, IRIX OS operating systems, etc.
In one embodiment, the computer system 110 is a personal computer, a laptop computer, a Blackberry® device, a portable computing device, a server, a computer workstation, a local area network of individual computers, an interactive kiosk, a personal digital assistant, an interactive wireless communications device, a handheld computer, an embedded computing device, or the like.
As can be appreciated by one of ordinary skill in the art, the computer system 110 may include various sub-routines, procedures, definitional statements, and macros. Each of the foregoing modules are typically separately compiled and linked into a single executable program. However, it is to be appreciated by one of ordinary skill in the art that the processes that are performed by selected ones of the modules may be arbitrarily redistributed to one of the other modules, combined together in a single module, made available in a shareable dynamic link library, or partitioned in any other logical way.
B. Computer System 120
In one embodiment, a second computer system 120 communicates with other computer systems 110, 130 via a network 102 as part of a computer cluster 100. In one embodiment, the computer system 120 is a personal computer, a workstation, a server, or a blade including one or more processors 122a-b, a memory device 124, an optional storage device 126, as well as a network interface module (not shown) for communications with the network 102.
1. Processors 112a-b 
In one embodiment, the computer system 120 includes one or more processors 122a-b. The processors 122a-b can be one or more general purpose single-core or multi-core microprocessors such as a Pentium® processor, a Pentium® II processor, a Pentium® Pro processor, a Pentium® III processor, Pentium® 4 processor, a Core Duo® processor, a Core 2 Duo® processor, a Xeon® processor, an Itanium® processor, a Pentium® M processor, an x86 processor, an Athlon® processor, an 8051 processor, a MIPS® processor, a PowerPC® processor, an ALPHA® processor, etc. In addition, the processors 122a-b can be any special purpose microprocessors such as a digital signal processor. The total number of processing cores (for example, processing units capable of single-threaded execution) within all processors 122a-b in the computer system 120 corresponds to the number of nodes available in the computer system 120. For example, if the processors 122a-b were each Core 2 Duo® processors having two processing cores, computer system 120 would have four nodes in all. Each node can run one or more instances of a program module, such as a single-threaded kernel module.
2. Network Interface Module
The computer system 120 can also include a network interface module (not shown) that facilitates communication between the computer system 120 and other computer systems 110, 130 via the communications network 102.
The network interface module can use a variety of network protocols. In one embodiment, the network interface module includes TCP/IP. However, it is to be appreciated that other types of network communication protocols such as, for example, Point-to-Point Protocol (“PPP”), Server Message Block (“SMB”), Serial Line Internet Protocol (“SLIP”), tunneling PPP, AppleTalk, etc., may also be used.
3. Memory 124 and Storage 126
The computer system 120 can include memory 124. Memory 124 can include, for example, processor cache memory (such as processor core-specific or cache memory shared by multiple processor cores), dynamic random-access memory (“DRAM”), static random-access memory (“SRAM”), or any other type of memory device capable of storing computer data, instructions, or program code. The computer system 120 can also include optional storage 126. Storage 126 can include, for example, one or more hard disk drives, floppy disks, flash memory, magnetic storage media, CD-ROMs, DVDs, optical storage media, or any other type of storage device capable of storing computer data, instructions, and program code.
4. Computer System 120 Information
The computer system 120 may be used in connection with various operating systems such as: Microsoft® Windows® 3.X, Windows 95®, Windows 98®, Windows NT®, Windows 2000®, Windows XP®, Windows CE®, Palm Pilot OS, OS/2, Apple® MacOS®, MacOS X®, MacOS X Server®, Disk Operating System (DOS), UNIX, Linux®, VxWorks, or IBM® OS/2®, Sun OS, Solaris OS, IRIX OS operating systems, etc.
In one embodiment, the computer system 120 is a personal computer, a laptop computer, a Blackberry® device, a portable computing device, a server, a computer workstation, a local area network of individual computers, an interactive kiosk, a personal digital assistant, an interactive wireless communications device, a handheld computer, an embedded computing device, or the like.
As can be appreciated by one of ordinary skill in the art, the computer system 120 may include various sub-routines, procedures, definitional statements, and macros. Each of the foregoing modules are typically separately compiled and linked into a single executable program. However, it is to be appreciated by one of ordinary skill in the art that the processes that are performed by selected ones of the modules may be arbitrarily redistributed to one of the other modules, combined together in a single module, made available in a shareable dynamic link library, or partitioned in any other logical way.
C. Computer System 130
In one embodiment, a third computer system 130 communicates with other computer systems 110, 120 via a network 102 as part of a computer cluster 100. In one embodiment, the computer system 130 is a personal computer, a workstation, a server, or a blade including one or more processors 132, a memory device 134, an optional storage device 136, as well as a network interface module (not shown) for communications with the network 102.
1. Processors 112a-b 
In one embodiment, the computer system 130 includes a processor 132. The processor 132 can be a general purpose single-core or multi-core microprocessors such as a Pentium® processor, a Pentium® II processor, a Pentium® Pro processor, a Pentium® III processor, Pentium® 4 processor, a Core Duo® processor, a Core 2 Duo® processor, a Xeon® processor, an Itanium® processor, a Pentium® M processor, an x86 processor, an Athlon® processor, an 8051 processor, a MIPS® processor, a PowerPC® processor, or an ALPHAS processor. In addition, the processor 132 can be any special purpose microprocessor such as a digital signal processor. The total number of processing cores (for example, processing units capable of single-threaded execution) within processor 132 in the computer system 130 corresponds to the number of nodes available in the computer system 130. For example, if the processor 132 was a Core 2 Duo® processor having two processing cores, the computer system 130 would have two nodes. Each node can run one or more instances of a program module, such as a single-threaded kernel module.
2. Network Interface Module
The computer system 130 can also include a network interface module (not shown) that facilitates communication between the computer system 130 and other computer systems 110, 120 via the communications network 102.
The network interface module can use a variety of network protocols. In one embodiment, the network interface module includes TCP/IP. However, it is to be appreciated that other types of network communication protocols such as, for example, Point-to-Point Protocol (“PPP”), Server Message Block (“SMB”), Serial Line Internet Protocol (“SLIP”), tunneling PPP, AppleTalk, etc., may also be used.
3. Memory 134 and Storage 136
The computer system 130 can include memory 134. Memory 134 can include, for example, processor cache memory (such as processor core-specific or cache memory shared by multiple processor cores), dynamic random-access memory (“DRAM”), static random-access memory (“SRAM”), or any other type of memory device capable of storing computer data, instructions, or program code. The computer system 130 can also include optional storage 136. Storage 136 can include, for example, one or more hard disk drives, floppy disks, flash memory, magnetic storage media, CD-ROMs, DVDs, optical storage media, or any other type of storage device capable of storing computer data, instructions, and program code.
4. Computer System 130 Information
The computer system 130 may be used in connection with various operating systems such as: Microsoft® Windows® 3.X, Windows 95®, Windows 98®, Windows NT®, Windows 2000®, Windows XP®, Windows CE®, Palm Pilot OS, OS/2, Apple® MacOS®, MacOS X®, MacOS X Server®, Disk Operating System (DOS), UNIX, Linux®, VxWorks, or IBM® OS/2®, Sun OS, Solaris OS, IRIX OS operating systems, etc.
In one embodiment, the computer system 130 is a personal computer, a laptop computer, a Blackberry® device, a portable computing device, a server, a computer workstation, a local area network of individual computers, an interactive kiosk, a personal digital assistant, an interactive wireless communications device, a handheld computer, an embedded computing device, or the like.
As can be appreciated by one of ordinary skill in the art, the computer system 130 may include various sub-routines, procedures, definitional statements, and macros. Each of the foregoing modules are typically separately compiled and linked into a single executable program. However, it is to be appreciated by one of ordinary skill in the art that the processes that are performed by selected ones of the modules may be arbitrarily redistributed to one of the other modules, combined together in a single module, made available in a shareable dynamic link library, or partitioned in any other logical way.
E. Communications Network 102
In one embodiment, computer systems 110, 120, 130 are in communication with one another via a communications network 102.
The communications network 102 may include one or more of any type of electronically connected group of computers including, for instance, the following networks: a virtual private network, a public Internet, a private Internet, a secure Internet, a private network, a public network, a value-added network, a wired network, a wireless network, an intranet, etc. In addition, the connectivity to the network can be, for example, a modem, Ethernet (IEEE 802.3), Gigabit Ethernet, 10-Gigabit Ethernet, Token Ring (IEEE 802.5), Fiber Distributed Datalink Interface (FDDI), Frame Relay, InfiniBand, Myrinet, Asynchronous Transfer Mode (ATM), or another interface. The communications network 102 may connect to the computer systems 110, 120, 130, for example, by use of a modem or by use of a network interface card that resides in each of the systems.
In addition, the same or different communications networks 102 may be used to facilitate communication between the first computer system 110 and the second computer system 120, between the first computer system 110 and the third computer system 130, and between the second computer system 120 and the third computer system 130.
III. Software Modules
As shown in FIGS. 1 and 2, one embodiment of a cluster system 100 includes a user interface module 202 that is able to access a plurality of kernel modules 206a-e by communicating with a first cluster node module 204a. User interface module can be stored in a memory 114, 124, 134 while running, for example, and/or can be stored in a storage device 116, 126, 136. The first cluster node module 204a is in communication with each of the other cluster node modules 204b-e. The kernel modules 206a-e can reside in the memory of one or more computer systems on which they run. For example, the memory 114 of the first computer system 110 can store instances of kernel modules 206a-b, the memory 124 of the second computer system 120 can store instances of kernel modules 206c-d, and the memory 134 of the third computer system 130 can store an instance of kernel module 206e. The kernel modules 206a-e, which include single-threaded program code, are each associated with one of the processors 112a, 112b, 122a, 122b, 132. A cluster configuration module stored on one or more of the computer systems 110, 120, 130 or on a remote computer system, for example, can establish communication with the cluster node modules 204a-e. In one embodiment, communication between the cluster configuration module 208 and the cluster node modules 204a-e initializes the cluster node modules 204a-e to provide cluster computing support for the computer cluster 100.
A. Cluster Node Module 204
In one embodiment, the cluster node modules 204a-e provide a way for many kernel modules 206a-e such as, for example, Mathematica kernels, running on a computer cluster 100 to communicate with one another. A cluster node module 204 can include at least a portion of an application programming interface (“API”) known as the Message-Passing Interface (“MPI”), which is used in several supercomputer and cluster installations. A network of connections (for example, the arrows shown in FIG. 2) between the cluster node modules 204a-e can be implemented using a communications network 102, such as, for example, TCP/IP over Ethernet, but the connections could also occur over any other type of network or local computer bus.
A cluster node module 204 can use an application-specific toolkit or interface such as, for example, Mathematica's MathLink, Add-Ons, or packets, to interact with an application. Normally used to connect a Mathematica kernel to a user interface known as the Mathematica Front End or other Mathematica kernels, MathLink is a bidirectional protocol to sends “packets” containing messages, commands, or data between any of these entities. MathLink does not allow direct cluster computing-like simultaneous communication between Mathematica kernels during execution of a command or thread. MathLink is also not designed to perform multiple simultaneous network connections. In some embodiments, a cluster node module 204 can use an application-specific toolkit such as, for example, MathLink, for connections between entities on the same computer.
When speaking about procedures or actions on a cluster or other parallel computer, not all actions happen in sequential order, nor are they required to. For example, a parallel code, as opposed to a single-processor code of the classic “Turing machine” model, has multiple copies of the parallel code running across the cluster, typically one for each processor (or “processing element” or “core”). Such parallel code is written in such a way that different instances of the same code can communicate, collaborate, and coordinate work with each other. Multiple instances of these codes can run at the same time in parallel.
If the count of the code instances is an integer N, each instance of code execution can be labeled 0 through N-1. For example, a computer cluster can include N connected computers, each containing a processor. The first has cluster node module 0 connected with kernel module 0 running on processor 0. The next is cluster node module 1 and kernel module 1, on processor 1, and so forth for each of the N connected computers. Some steps of their procedure are collaborative, and some steps are independent. Even though these entities are not necessarily in lock-step, they do follow a pattern of initialization, main loop behavior (for example, cluster node module operation), and shut down.
In contrast, a parallel computing toolkit (PCT) that is provided as part of the gridMathematica software package does not provide a means for instances of the same code running on different nodes to communicate, collaborate, or coordinate work among the instances. The PCT provides commands that connect Mathematica kernels in a master-slave relationship rather than a peer-to-peer relationship as enabled by some embodiments disclosed herein. A computer cluster having peer-to-peer node architecture performs computations that can be more efficient, easier to design, and/or more reliable than similar computations performed on grid computers having master-slave node architecture. Moreover, the nature of some computations may not allow a programmer to harness multi-node processing power on systems that employ master-slave node architecture.
FIG. 3 shows one embodiment of a cluster node module 204 implementing MPI calls and advanced MPI functions. In the embodiment shown in FIG. 3, cluster node module 204 includes MPI module 302, advanced functions module 304, received message queue 306, and message receiving queue 308.
1. MPI module 302
In one embodiment, the cluster node module 204 includes an MPI module 302. The MPI module 302 can include program code for one or more of at least five kinds of MPI instructions or calls. Selected constants, instructions, and/or calls that can be implemented by the MPI module 302 are as follows:
MPI Constants
Node identifiers are used to send messages to nodes or receive messages from them. In MPI, this is accomplished by assigning each node a unique integer ($IdProc) starting with 0. This data, with a knowledge of the total count ($NProc), makes it possible to programmatically divide any measurable entity.








TABLE A





Constant
Description







$IdProc
The identification number of the current processor


$NProc
The number of processors in the current cluster


$mpiCommWorld
The communicator world of the entire cluster



(see MPI Communicator routines, below)


mpiCommWorld
The default communicator world for the high-



level routines.









Basic MPI Calls

In one embodiment, the MPI module 302 can include basic MPI calls such as, for example, relatively low-level routines that map MPI calls that are commonly used in other languages (such as C and Fortran), so that such calls can be available directly from the Mathematica user interface 204. In some embodiments, basic MPI calls include calls that send data, equations, formulas, and/or other expressions.
Simply sending expressions from one node to another is possible with these most basic MPI calls. One node can call to send an expression while the other calls a corresponding routine to receive the sent expression. Because it is possible that the receiver has not yet called mpiRecv even if the message has left the sending node, completion of mpiSend is not a confirmation that it has been received.








TABLE B





Call
Description







mpiSend[expr, target,
Sends an expression expr to a node with


comm, tag]
the ID target in the communicator would



comm, waiting until that expression has



left this kernel


mpiRecv [expr, target,
Receives an expression into expr from a


comm, tag]
node with the ID target in the communicator



world comm, waiting until the expression



has arrived


mpiSendRecv[sendexpr,
Simultaneously sends the expression


dest, recvexpr, source,
sendexpr to the node with the ID target


comm]
and receives an expression into recvexpr



from the node with the ID source in the



communicator world comm, waiting until



both operations have returned.









Asynchronous MPI Calls

Asynchronous calls make it possible for the kernel to do work while communications are proceeding simultaneously. It is also possible that another node may not be able to send or receive data yet, allowing one kernel to continue working while waiting.








TABLE C





Call
Description







mpiISend[expr, target,
Sends an expression expr to a processor


comm, tag, req]
with the ID target in the communicator



world comm, returning immediately. It can



be balanced with calls to mpiTest[req]



until mpiTest[req] returns True.


mpiIRecv[expr, target,
Receives an expression expr from a proessor


comm, tag, req]
with the ID target in the communicator



world comm, returning immediately. It can



be balanced with calls to mpiTest[req]



until mpiTest[req] returns True. The expr



is not safe to access until mpiTest[req]



returns True.


mpiTest[req]
Completes asynchronous behavior of mpiISend



and mpiIRecv


mpWait[req]
Calls mpiTest until it returns True.


mpiWaitall[reglist]
Calls mpiWait all on every element of reqlist


mpiWaitany[reqlist]
Calls mpiTest on each element of realist



until one of them returns True









The mpiISend[ ] command can be called from within a kernel module 206 (for example, a Mathematica kernel). It creates a packet containing the Mathematica expression to be sent as payload and where the expression should be sent. The packet itself is destined only for its local cluster node module. Once received by its local cluster node module, this packet is decoded and its payload is forwarded on to the cluster node module specified in the packet.
The mpiIRecv[ ] command can also be called from within a kernel module 206. It creates a packet specifying where it expects to receive an expression and from which processor this expression is expected. Once received by its local cluster node module, this packet is decoded and its contents are stored in a message receiving queue (MRQ) 308 (FIG. 3).
The mpiTest[ ] command can be called from within a kernel module 206. It creates a packet specifying which message to test for completion, then waits for a reply expression to evaluate. Once received by the kernel module's associated cluster node module 204, this packet is decoded and its message specifier is used to search for any matching expressions listed as completed in its received message queue (RMQ) 306. If such completed expressions are found, it is sent to its local kernel module as part of the reply in mpiTest[ ]. The kernel module receives this reply expression and evaluates it, which updates the kernel module's variables as needed.
Other MPI calls are built on the fundamental calls mpiISend, mpiIRecv, and mpiTest. For example, mpiBcast, a broadcast, creates instructions to send information from the broadcast processor to all the others, while the other processors perform a Recv. Similarly, high-level calls of the toolkit can be built on top of the collection of MPI calls.
Collective MPI Calls
In one embodiment, the MPI module 302 can include program code for implementing collective MPI calls (for example, calls that provide basic multi-node data movement across nodes). Collective MPI calls can include broadcasts, gathers, transpose, and other vector and matrix operations, for example. Collective calls can also provide commonly used mechanisms to send expressions between groups of nodes.








TABLE D





Call
Description







mpiBcast[expr, root,
Performs a broadcast of expr from the root


comm]
processor to all the others in the



communicator world comm. An expression is



expected to be supplied by the root



processor, while all the others expect expr



to be overwritten by the incoming expression.


mpiGather[sendexpr,
All processors (including root) in the


recvexpr, root, comm]
communicator comm send their expression in



sendexpr to the root processor, which



produces a list of these expressions, in



the order according to comm, in recvexpr.



On the processors that are not root,



recvexpr is ignored.


mpiAllgather[sendexpr,
All processors in the communicator comm send


recvexpr, comm]
their expression in sendexpr, which are



organized into a list of these expressions,



in the order according to comm, in recvexpr



on all processors in comm.


mpiScatter[sendexpr,
Processor root partitions the list in sendexpr


recvexpr, root, comm]
into equal parts (if possible) and places each



piece in recvexpr on all the processors



(including root) in the communicator world



comm, according the order and size of comm.


mpiAlltoall[sendexpr,
Each processor sends equal parts of the


recvexpr, comm]
list in sendexpr to all other processors



in the communicator world comm, which each



collects from all other processors are



organizes into the order according to comm.









In one embodiment, the MPI module 302 includes program code for implementing parallel sums and other reduction operations on data stored across many nodes. MPI module 302 can also include program code for implementing simple parallel input/output calls (for example, calls that allow cluster system 200 to load and store objects that are located on a plurality of nodes).








TABLE E





Call
Description







mpiReduce[sendexpr,
Performs a collective reduction operation


recvexpr, operation, root,
between expressions on all processors in


comm]
the communicator world comm for every



element in the list in sendexpr returning



the resulting list in recvexpr on the



processor with the ID root.


mpiAllreduce[sendexpr,
Performs a collective reduction operation


recvexpr, operation,
between expressions on all processors in


comm]
the communicator world comm for every



element in the list in sendexpr returning



the resulting list in recvexpr on every



processor.


mpiReduceScatter
Performs a collective reduction operation


[sendexpr, recvexpr,
between expressions on all processors in


operation, comm]
the communicator world comm for every



element in the list in sendexpr, partition-



ing the resulting list into pieces for each



processor's recvexpr.









These additional collective calls perform operations that reduce the data in parallel. The operation argument can be one of the constants below.








TABLE F





Constant
Description







mpiSum
Specifies that all the elements on different processors be



added together in a reduction call


mpiMax
Specifies that the maximum of all the elements on different



processors be chosen in a reduction call


mpiMin
Specifies that the minimum of all the elements on different



processors be chosen in a reduction call









MPI Communicator Calls

In one embodiment, the MPI module 302 includes program code for implementing communicator world calls (for example, calls that would allow subsets of nodes to operate as if they were a sub-cluster). Communicators organize groups of nodes into user-defined subsets. The communicator values returned by mpiCommSplit[ ] can be used in other NPI calls instead of mpiCommWorld.








TABLE G





Call
Description







mpiCommSize[comm]
Returns the number of processors within



the communicator comm


mpiCommRank[comm]
Returns the rank of this processor in



the communicator comm


mpiCommDup[comm]
Returns a duplicate communicator of



the communicator comm


mpiCommSplit[comm,
Creates a new communicator into several


color, key]
disjoint subsets each identified by



color. The sort order within each subset



is first by key, second according to the



ordering in the previous communicator.



Processors not meant to participate in



any new communicator indicates this by



passing the constant mpiUndefined. The



corresponding communicator is returned



to each calling processor.


mpiCommMap[comm]
Returns the mapping of the communicator


mpiCommMap[comm,
comm to the processor indexed according


target]
to $mpiCommWorld. Adding a second



argument returns just the ID of the



processor with the ID target in the



communicator comm.


mpiCommFree[comm]
Frees the communicator comm









Other MPI Support Calls

Other calls that provide common functions include:








TABLE H





Call
Description







mpiWtime[ ]
Provides wall-dock time since some fixed time



in the past. There is no guarantee that this



time will read the same on all processors.


mpWtick[ ]
Returns the time resolution of mpiWtime[ ]


MaxByElement[in]
For every nth element of each list of the list



in, chooses the maximum according to Max[ ],



and returns the result as one list. Used in the



mpiMax reduction operation.


MinByElement[in]
For every nth element of each list of the list



in, chooses the minimum according to Min[ ],



and returns the result as one list. Used in the



mpiMin reduction operation.









2. Advanced Functions Module 304
In one embodiment, the cluster node module 204 includes an advanced functions module 304. The advanced functions module 304 can include program code that provides a toolkit of functions inconvenient or impractical to do with MPI instructions and calls implemented by the MPI module 302. The advanced functions module 304 can rely at least partially on calls and instructions implemented by the MPI module 302 in the implementation of advanced functions. In one embodiment, the advanced functions module 304 includes a custom set of directives or functions. In an alternative embodiment, the advanced functions module 304 intercepts normal Mathematica language and converts it to one or more functions optimized for cluster execution. Such an embodiment can be easier for users familiar with Mathematica functions to use but can also complicate a program debugging process. Some functions implemented by the advanced functions module 304 can simplify operations difficult or complex to set up using parallel computing. Several examples of such functions that can be implemented by the advanced functions module 304 are shown below.
Built on the MPI calls, the calls that are described below provide commonly used communication patterns or parallel versions of Mathematica features. Unless otherwise specified, these are executed in the communicator mpiCommWorld, whose default is $mpiCommWorld, but can be changed to a valid communicator at run time.
Common Divide-and-Conquer Parallel Evaluation
In one embodiment, the advanced functions module 304 includes functions providing for basic parallelization such as, for example, routines that would perform the same operations on many data elements or inputs, stored on many nodes. These functions can be compared to parallelized for-loops and the like. The following calls address simple parallelization of common tasks. In the call descriptions, “expr” refers to an expression, and “loopspec” refers to a set of rules that determine how the expression is evaluated. In some embodiments, the advanced functions module 304 supports at least three forms of loopspec, including {var, count}, where the call iterates the variable var from 1 to the integer count; {var, start, stop}, where the call iterates the variable var every integer from start to stop; and {var, start, stop, increment}, where the call iterates the variable var from start adding increment for each iteration until var exceeds stop, allowing var to be a non-integer.








TABLE I





Call
Description







ParallelDo[expr, loopspec]
Like Do[ ] except that it evaluates



expr across the cluster, rather than on



just one processor. The rules for how



expr is evaluated is specified in



loopspec, like in Do[ ].


ParallelFunctionToList[f,
Evaluates the function f[i] from 1


count]
to count, but across the cluster, and


ParallelFunctionToList[f,
returns these results in a list. The


count, root]
third argument has it gather this list



into the processor whose ID is root.


ParallelTable[expr,
Like Table[ ] except that it


loopspec]
evaluates expr across the cluster,


ParallelTable[expr,
rather than on just one processor,


loopspec, root]
returning the locally evalulated



portion. The third argument has it



gather this table in to the



processor whose ID is root.


ParallelFunction[f, inputs,
Like f[inputs] except that it


root]
evaluates f on a subset of inputs



scattered across the cluster from



processor root and gathered back



to root.


ParallelNintegrate[expr,
Like Nintegrate[ ] except that


loopspec]
it evaluates a numerical integration


ParallelNintegrate[expr,
of expr over domains partitioned


loopspec, digits]
into the number of processors



in the cluster, then returns the



sum. The third argument has each



numerical integration execute with



at least that many digits of



precision.









Guard-Cell Management

In one embodiment, the advanced functions module 304 includes functions providing for guard-cell operations such as, for example, routines that perform nearest-neighbor communications to maintain edges of local arrays in any number of dimensions (optimized for 1-, 2-, and/or 3-D). Typically the space of a problem is divided into partitions. Often, however, neighboring edges of each partition can interact, so a “guard cell” is inserted on both edges as a substitute for the neighboring data. Thus the space a processor sees is two elements wider than the actual space for which the processor is responsible. EdgeCell helps maintain these guard cells.








TABLE J





Call
Description







EdgeCell[list]
Copies the second element of list to the last



element of the left processor and the second-to-



last element of list to the first element of the



right processor while simultaneously receiving the



same from its neighbors.









Matrix and Vector Manipulation

The advanced functions module 304 can also include functions providing for linear algebra operations such as, for example, parallelized versions of basic linear algebra on structures partitioned on many nodes. Such linear algebra operations can reorganize data as needed to perform matrix and vector multiplication or other operations such as determinants, trace, and the like. Matrices are partitioned and stored in processors across the cluster. These calls manipulate these matrices in common ways.








TABLE K





Call
Description







ParallelTranspose[matrix]
Like Transpose[ ] except that it transposes matrix that is in fact



represented across the cluster, rather than on just one



processor. It returns the portion of the transposed matrix



meant for that processor.


ParallelProduct[matrix,
Evaluates the product of matrix and vector, as it would on one


vector]
processor, except that matrix is represented across the cluster.


ParallelDimensions[matrix]
Like Dimensions[ ] except that matrix is represented across the



cluster, rather than on just one processor. It returns a list of



each dimension.


ParallelTr[matrix]
Like Tr[ ] except that the matrix is represented across the



cluster, rather than on just one processor. It returns the trace



of this matrix.


ParallelIdentity[rank]
Like Identity[ ], it generates a new identity matrix, except that



the matrix is represented across the cluster, rather than on just



one processor. It returns the portion of the new matrix for this



processor.


ParallelOuter[f, vector1,
Like Outer[f, vector1, vector2] except that the answer


vector2]
becomes a matrix represented across the cluster, rather than



on just one processor. It returns the portion of the new matrix



for this processor.


ParallelInverse[matrix]
Like Inverse[ ] except that the matrix is represented across the



cluster, rather than on just one processor. It returns the inverse



of the matrix.









Element Management

In one embodiment, the advanced functions module 304 includes element management operations. For example, a large bin of elements or particles cut up in space across the nodes may need to migrate from node to node based on rules or criteria (such as their spatial coordinate). Such operations would migrate the data from one node to another. Besides the divide-and-conquer approach, a list of elements can also be partitioned in arbitrary ways. This is useful if elements need to be organized or sorted onto multiple processors. For example, particles of a system may drift out of the space of one processor into another, so their data would need to be redistributed periodically.








TABLE L





Call
Description







ElementManage[list, switch]
Selects which elements of list will be sent to which



processors according to the function switch[ ] is evaluated on



each element of list. If switch is a function, switch[ ] should



return the ID of the processor that element should be sent. If



switch is an integer, the call assumes that each elements is



itself a list, whose first element is a number ranging from 0



to the passed argument. This call returns a list of the



elements, from any processor, that is switch selected for this



processor.


ElementManage[list]
Each element of list can be a list of two elements, the first



being the ID of the processor where the element should be



sent, while the second is arbitrary data to send. This call



returns those list elements, from any and all processors,



whose first element is this processors ID in a list. This call is



used internally by the two-argument version of ElementManage[].









Fourier Transform

In one embodiment, the advanced functions module 304 includes program code for implementing large-scale parallel fast Fourier transforms (“FFTs”). For example, such functions can perform FFTs in one, two, and/or three dimensions on large amounts of data that are not stored on one node and that are instead stored on many nodes. Fourier transforms of very large arrays can be difficult to manage, not the least of which is the memory requirements. Parallelizing the Fourier transform makes it possible to make use of all the memory available on the entire cluster, making it possible to manipulate problem sizes that no one processor could possibly do alone.









TABLE M






Call
Description








ParallelFourier[list]
Like Fourier[ ] except that list is a




two- or three-dimensional list represented




across the cluster, like for matrices,




above. It returns the portion of the




Fourier-transformed array meant for that




processor.









Parallel Disk I/O

In one embodiment, the advanced functions module 304 includes parallel disk input and output calls. For example, data may need to be read in and out of the cluster in such a way that the data is distributed across the cluster evenly. The calls in the following table enable the saving data from one or more processors to storage and the retrieval data from storage.








TABLE N





Call
Description







ParallelPut[expr,
Puts expr into the file with the name filename in order on


filename]
processor 0. The third argument specifies that the file be written


ParallelPut[expr, filename
on the processor whose ID is root. The fourth uses the


root]
communicator world comm.


ParallelPut[expr, filename,



root, comm]



ParallelGet[filename]
Reads and returns data from the file with the name filename on


ParallelGet[filename,
processor 0 partitioned into each processor on the cluster. The


root]
second argument specifies that the file is to be read on the


ParallelGet[filename,
processor whose ID is root. The third uses the communicator


root, comm]
world comm.


ParallelBinaryPut[expr,
Puts expr into the file with the binary format type with the name


type, filename]
filename in order on processor 0. The fourth argument specifies


ParallelBinaryPut[expr,
that the file be written on the processor whose ID is root. The


filename, root]
fifth uses the communicator world comm.


ParallelBinaryPut[expr,



filename, root, comm]



ParallelBinaryGet[type,
Reads and returns data in the binary format type from the file


filename]
with the name filename on processor 0 partitioned into each


ParallelBinaryGet[type,
processor on the cluster. The third argument specifies that the


filename, root]
file is to be read on the processor whose ID is root. The fourth


ParallelBinaryGet[type,
uses the communicator world comm.


filename, root, comm]



ParallelGetPerProcessor
Puts expr into the file with the name filename in order on


[expr, filename]
processor 0, one line per processor. The third argument specifies


ParallelGetPerProcessor
that the file be written on the processor whose ID is root. The


[filename, root]
fourth uses the communicator world comm.


ParallelGetPerProcessor



[filename, root, comm]



ParallelGetPerProcessor
Reads and returns data from the file with the name filename on


[filename]
processor 0, one line for each processor. The second argument


ParallelGetPerProcessor
specifies that the file is to be read on the processor whose ID is


[filename, root]
root. The third uses the communicator world comm.


ParallelGetPerProcessr



[filename, root, comm]









Automatic Load Balancing

Some function calls can take an inconsistent amount of processing time to complete. For example, in Mathematica, the call f[20] could in general take much longer to evaluate than f[19]. Moreover, if one or more processors within the cluster are of different speeds (for example, if some operate at a core frequency of 2.6 GHz while other operate at less than one 1 GHz), one processor may finish a task sooner than another processor.
In some embodiments, the advanced functions module 304 includes a call that can improve the operation of the computer cluster 100 in such situations. In some embodiments, the root processor assigns a small subset of the possible calls for a function to each processor on the cluster 100. Whichever processor returns its results first is assigned a second small subset of the possible calls. The root processor will continue to assign small subsets of the possible calls as results are received until an evaluation is complete. The order in which the processors finish can vary every time an expression is evaluated, but the root processor will continue assigning additional work to processors as they become available.
In one illustrative example, there are 4 processors and f[1] to f[100] to evaluate. One could implement this by assigning f[1], f[2], f[3], f[4] to each of processors 0 (the root can assign to oneself) through 3. If the f[2] result came back first, then processor 1 would be assigned f[5]. If the f[4] result is returned next, f[6] would be assigned to processor 3. The assignments continue until all results are calculated. The results are organized for output back to the user.
In alternative embodiments, the subsets of possible calls can be assigned in any order, rather than sequentially, or in batches (for example, f[1], f[5], f[9] assigned to processor 1, etc.). Also, the subsets could be organized by delegation. For example, one processor node may not necessarily be in direct control of the other processors. Instead, a large subset could be assigned to a processor, which would in turn assign subsets of its work to other processors. The result would create a hierarchy of assignments like a vast army.








TABLE O







LoadBalanceFunctionToList[f,
Evaluates the function f[i] from 1


count]
to count, but across the cluster


LoadBalanceFunctionToList[f,
using load-balancing techniques, and


count, root]
returns these results in a list. The



third argument has it gather this list



into the processor whose ID is root.









3. Received Message Queue 306
In one embodiment, the cluster node module 204 includes a received message queue 306. The received message queue 306 includes a data structure for storing messages received from other cluster node modules. Related data pertaining to the messages received, such as whether an expression has been completed, may also be stored in the received message queue 306. The received message queue 306 may include a queue and/or another type of data structure such as, for example, a stack, a linked list, an array, a tree, etc.
4. Message Receiving Queue 308
In one embodiment, the cluster node module 204 includes a message receiving queue 308. The message receiving queue 308 includes a data structure for storing information about the location to which an expression is expected to be sent and the processor from which the expression is expected. The message receiving queue 308 may include a queue and/or another type of data structure such as, for example, a stack, a linked list, an array, a tree, etc.
B. Cluster Configuration Module 208
Cluster configuration module 208 includes program code for initializing a plurality of cluster node modules to add cluster computing support to computer systems 110, 120, 130. U.S. Pat. No. 7,136,924, issued to Dauger (the “'924 patent”), the entirety of which is hereby incorporated by reference and made a part of this specification, discloses a method and system for parallel operation and control of computer clusters. One method generally includes obtaining one or more personal computers having an operating system with discoverable of network services. In some embodiments, the method includes obtaining one or more processors or processor cores on which a kernel module can run. As described in the '924 patent, a cluster node control and interface (CNCI) group of software applications is copied to each node. When the CNCI applications are running on a node, the cluster configuration module 208 can permit a cluster node module 204, in combination with a kernel module 206, to use the node's processing resources to perform a parallel computation task as part of a computer cluster. The cluster configuration module 208 allows extensive automation of the cluster creation process in connection with the present disclosure.
C. User Interface Module 202
In some embodiments, computer cluster 100 includes a user interface module 202, such as, for example a Mathematica Front End or a command line interface, that includes program code for a kernel module 206 to provide graphical output, accept graphical input, and provide other methods of user communication that a graphical user interface or a command-line interface provides. To support a user interface module 202, the behavior of a cluster node module 204a is altered in some embodiments. Rather than sending output to and accepting input from the user directly, the user interface module 202 activates the cluster node module 204a to which it is connected and specifies parameters to form a connection, such as a MathLink connection, between the cluster node module 204a and the user interface module 202. The user interface module's activation of the cluster node module 204a can initiate the execution of instructions to activate the remaining cluster node modules 204b-e on the cluster and to complete the sequence to start all kernel modules 206a-e on the cluster. Packets from the user interface module 202, normally intended for a kernel module 206a, are accepted by the cluster node module 204a as a user command. Output from the kernel module 206a associated with the cluster node module 204a can be forwarded back to the user interface module 202 for display to a user. Any of the cluster node modules 204a-e can be configured to communicate with a user interface module 202.
D. Kernel Module 206
A kernel module 206 typically includes program code for interpreting high-level code, commands, and/or instructions supplied by a user or a script into low-level code, such as, for example, machine language or assembly language. In one embodiment, each cluster node module 204a-e is connected to all other cluster node modules, while each kernel module 206a-e is allocated and connected only to one cluster node module 204. In one embodiment, there is one cluster node module-kernel module pair per processor. For example, in an embodiment of a computer cluster 100 including single-processor computer systems, each cluster node module-kernel module pair could reside on a single-processor computer. If a computer contains multiple processors or processing cores, it may contain multiple cluster node module-kernel module pairs, but the pairs can still communicate over the cluster node module's network connections.
IV. Cluster Computing Methods
In one embodiment, the computer cluster 100 includes a cluster initialization process, a method of cluster node module operation, and a cluster shut down process.
A. Cluster Initialization Process
In one embodiment, a cluster configuration module 202 initializes one or more cluster node modules 204 in order to provide cluster computing support to one or more kernel modules 206, as shown in FIG. 4.
At 402, cluster node modules are launched on the computer cluster 100. In one embodiment, the cluster node module 204a running on a first processor 112a (for example, where the user is located) accesses the other processors 112b, 122a-b, 132 on the computer cluster 100 via the cluster configuration module 208 to launch cluster node modules 204b-e onto the entire cluster. In an alternative embodiment, the cluster configuration module 208 searches for processors 112a-b, 122a-b, 132 connected to one another via communications network 102 and launches cluster node modules 204a-e on each of the processors 112a-b, 122a-b, 132.
The cluster node modules 204a-e establish communication with one another at 404. In one embodiment, each of the cluster node modules 204a-e establish direct connections using the MPI_Init command with other cluster node modules 204a-e launched on the computer cluster 100 by the cluster configuration module 208.
At 406, each cluster node module 204 attempts to connect to a kernel module 206. In one embodiment, each instance of the cluster node modules 204a-e locates, launches, and connects with a local kernel module via MathLink connections and/or similar connection tools, for example, built into the kernel module 206.
At 408, the cluster node modules 204 that are unconnected to a kernel module 206 are shut down. In one embodiment, each cluster node module 204 determines whether the local kernel module cannot be found or connected to. In one embodiment, each cluster node module 204 reports the failure to connect to a kernel module 206 to the other cluster node modules on computer cluster 100 and quits.
Processor identification numbers are assigned to the remaining cluster node modules 204 at 410. In one embodiment, each remaining cluster node module 204 calculates the total number of active processors (N) and determines identification numbers describing the remaining subset of active cluster node modules 204a-e and kernel modules 206a-e. This new set of cluster node module-kernel module pairs may be numbered 0 through N-1, for example.
Message passing support is initialized on the kernel modules 206a-e at 412. In one embodiment, each cluster node module 204 supplies initialization code (for example, Mathematica initialization code) to the local kernel module 206 to support message passing.
Finally, at 414, the cluster node modules 204a-e enter a loop to accept user entry. In one embodiment, a main loop (for example, a cluster operation loop) begins execution after the cluster node module 204a on the first processor 112a returns to user control while each of the other cluster node modules 204 waits for messages from all other cluster node modules 204a-e connected to the network 102.
The initialization process creates a structure enabling a way for the kernel modules 206a-e to send messages to one another. In some embodiments, any kernel module can send data to and receive data from any other kernel module within the cluster when initialization is complete. The cluster node module creates an illusion that a kernel module is communicating directly with the other kernel modules. The initialization process can create a relationship among kernel modules on a computer cluster 100 such as the one shown by way of example in FIG. 2.
B. Cluster Node Module Operation
In one embodiment, a cluster node module 204 implements cluster computing support for a kernel module 206 during a main loop, as shown in FIG. 5.
At 502, cluster node modules 204 wait for user commands or messages from other cluster node modules. In one embodiment, the cluster node module 204a connected to the user interface module 202 waits for a user command, while the other cluster node modules 204b-e continue checking for messages.
Once a command or message is received, the method proceeds to 504. At 504, the cluster node module 204a determines whether the message received is a quit command. If a quit command is received, the cluster node module 204a exits the loop and proceeds to a cluster node module shut down process at 505. If the message received is not a quit command, the process continues to 506.
At 506, received commands are communicated to all cluster node modules 204a-e on the computer cluster 100. In one embodiment, when a user enters a command in the user interface module 202, the cluster node module 204a connected to the user interface module 202 submits the user command to all other cluster node modules 204b-e in the computer cluster 100. The user commands can be simple (for example, “1+1”), but can also be entire subroutines and sequences of code (such as, for example, Mathematica code), including calls to MPI from within the user interface module 202 (for example, the Mathematica Front End) to perform message passing between kernel modules 206a-e (for example, Mathematica kernels). These include the fundamental MPI calls, which are implemented using specially identified messages between a cluster node module 204 and its local kernel module 206.
The message (or user command) is communicated to the kernel modules 206a-e at 508. In one embodiment, the cluster node module 204a connected to the user interface module 202 submits the user command to the kernel module 206a to which it is connected. Each of the other cluster node modules 204b-e, after receiving the message, submits the command to the respective kernel module 206b-e to which it is connected.
At 510, a cluster node module 204 receives a result from a kernel module 206. In one embodiment, once the kernel module 206 completes its evaluation, it returns the kernel module's output to the cluster node module 204 to which it is connected. Depending on the nature of the result from the kernel module, the cluster node module 204 can report the result to a local computer system or pass the result as a message to another cluster node module 204. For example, the cluster node module 204a running on the first processor 112a reports the output on its local computer system 110. For example, on the first processor 112a, cluster node module 204a only directly reports the output of kernel module 206a.
Messages from other cluster node modules 204 are responded to at 512. In one embodiment, each cluster node module (for example, the cluster node module 204a) checks for and responds to messages from other cluster node modules 204b-e and from the kernel module 206a repeatedly until those are exhausted. In one embodiment, output messages from the kernel module 206 are forwarded to output on the local computer system. Messages from other cluster node modules 204 are forwarded to a received message queue 306 (“RMQ”). Data from each entry in the message receiving queue 308 (“MRQ”) is matched with entries in the RMQ 306 (see, for example, description of the mpiIRecv[ ] call, above). If found, data from the MRQ 308 are combined into those in the RMQ 306 and marked as “completed” (see, for example, description of the mpiTest[ ] call, above). This process provides the peer-to-peer behavior of the cluster node modules 204a-e. Via this mechanism, code running within multiple, simultaneously running kernel modules (for example, Mathematica kernels) can interact on a pair-wise or collective basis, performing calculations, processing, or other work on a scale larger and/or faster than one kernel could have done alone. In this manner, user-entered instructions and data specifying what work will be done via user commands can be executed more quickly and/or reliably. Once responding to messages has completed, the process returns to 502.
C. Cluster Shut Down Process
In one embodiment, a computer cluster 100 includes a procedure to shut down the system. If the operation process (or main loop) on the cluster node module 204a connected to the user interface module 202 detects a “Quit” or “Exit” command or otherwise receives a message from the user indicating a shut down, the sequence to shut down the cluster node modules 204a-e and the kernel modules 206a-e is activated. In one embodiment, the cluster node module 204a connected to the user interface module 202 sends a quit message to all other cluster node modules 204b-e. Each cluster node module 204 forwards the quit command to its local kernel module 206. Once its Mathematica kernel has quit, each cluster node module 204 proceeds to tear down its communication network with other cluster node modules (for example, see description of the MPI_Finalize command, above). At the conclusion of the process, each cluster node module 204 exits execution.
V. Example Operation
For purposes of illustration, sample scenarios are discussed in which the computer cluster system is used in operation. In these sample scenarios, examples of Mathematica code are given, and descriptions of how the code would be executed by a cluster system are provided.
Basic MPI
Fundamental data available to each node includes the node's identification number and total processor count.

    
    
        In[1]:={$IdProc, $NProc}
        Out[1]:={0, 2}
    
    


The first element should be unique for each processor, while the second is generally the same for all. Processor 0 can see what other values are using a collective (see below) communications call such as mpiGather[ ].

    
    
        In[2]:=mpiGather[{$IdProc, $NProc},list,0]; list
        Out[2]:={{0, 2}, {1, 2}}

Peer-to-Peer MPI

    
    


The mpiSend and mpiRecv commands make possible basic message passing, but one needs to define which processor to target. The following defines a new variable, targetProc, so that each pair of processors will point to each other.

    
    
        In[3]:=targetProc=If[1==Mod[$IdProc, 2],$IdProc−1, $IdProc+1]
        Out[3]:=1
    
    


In this example, the even processors target its “right” processor, while the odd ones point its “left.” For example, if the processors were lined up in a row and numbered in order, every even-numbered processor would pair with the processor following it in the line, and every odd-numbered processor would pair with the processor preceding it. Then a message can be sent:

    
    
        In[4]:=If [1==Mod[ $IdProc,
        2],mpiSend[N[Pi,22],targetProc, mpiCommWorld,d], mpiRecv[a,targetProc,mpiCommWorld,d]]
    
    


The If [ ] statement causes the processors to evaluate different code: the odd processor sends 22 digits of Pi, while the even receives that message. Note that these MPI calls return nothing. The received message is in the variable a:

    
    
        In[5]:=a
        Out[5]:=3.1415926535897932384626
        In[6]:=Clear[a]
    
    


The variable a on the odd processors would have no definition. Moreover, if $NProc is 8, processor 3 sent Pi to processor 2, processor 5 sent Pi to processor 4, and so on. These messages were not sent through processor 0, but they communicated on their own.
The mpiISend and mpiIRecv commands have a letter “I” to indicate asynchronous behavior, making it possible to do other work while messages are being sent and received, or if the other processor is busy. So, the above example could be done asynchronously:

    
    
        In[7]:=If[1==Mod[$IdProc, 2],mpiISend[N[Pi,22],targetProc, mpiCommWorld,d,e], mpiIRecv[a,targetProc,mpiCommWorld,d,e]]
    
    


The variable e has important data identifying the message, and mpiTest[e] can return True before the expressions are to be accessed. At this point, many other evaluations can be performed. Then, one can check using mpiTest when the data is needed:

    
    
        In[29]:=mpiTest[e]
        Out[29]:=True
        In[30]:=a
        Out[30]:=3.1415926535897932384626
        In[31]:=Clear[a,e]
    
    


The mpiWait[e] command could have also have been used, which does not return until mpiTest[e] returns True. The power of using these peer-to-peer calls is that it becomes possible to construct any message-passing pattern for any problem.
Collective MPI
In some cases, such explicit control is not required and a commonly used communication pattern is sufficient. Suppose processor 0 has an expression in b that all processors are meant to have. A broadcast MPI call would do:

    
    
        In[8]:=mpiBcast[b, 0, mpiCommWorld]
    
    


The second argument specifies which processor is the “root” of this broadcast; all others have their b overwritten. To collect values from all processors, use mpiGatherD:

    
    
        In[9]:=mpiGather[b, c, 0, mpiCommWorld]
    
    


The variable c of processor 0 is written with a list of all the b of all the processors in mpiCommWorld. The temporal opposite is mpiScatter:

    
    
        In[10]:=Clear[b]; a={2, 4, 5, 6}; mpiScatter[a, b, 0, mpiCommWorld]; b
        Out [10]:={2, 4}
    
    


The mpiScatter command cuts up the variable a into even pieces (when possible) and scatters them to the processors. This is the result if $NProc=2, but if $NProc=4, b would only have {2}.
MPI provides reduction operations to perform simple computations mixed with messaging. Consider the following:

    
    
        In[11]:=a={{2+$IdProc, 45[ ],3, {1+$IdProc, $NProc[ ][ ]; mpiReduce [a,d,mpiSum, 0,mpiCommWorld]
        In[12]:=d
        Out[12]:={{5, 90}, 6, {3, 4}}
    
    


The mpiSum constant indicates that variable a of every processor will be summed. In this case, $NProc is 2, so those elements that were not identical result in odd sums, while those that were the same are even.
Most of these calls have default values if not all are specified. For example each of the following calls will have the equivalent effect as the above mpiGather[ ] call:

    
    
        mpiGather[b, c, 0]
        mpiGather[b, c]
        c=mpiGather[b]

High-Level Calls

    
    


High-level calls can include convenient parallel versions of commonly used application program calls (for example, Mathematica calls). For example, ParallelTable[ ] is like Table[ ], except that the evaluations are automatically performed in a distributed manner:

    
    
        In[13]:=ParallelTable[i,{i,100},0]
        Out[13]:={1,2,3,4,5, . . . ,99,100}
    
    


The third argument specifies that the answers are collated back to processor 0. This is a useful, simple way to parallelize many calls to a complex function. One could define a complicated function and evaluate it over a large range of inputs:

    
    
        In[14]:=g[x_]:=Gamma[2+0.5*(x−1)]; ParallelTable[g[i],{i,100},0]
        Out[14]:={1, 1.32934, 2., 3.32335, 6., 11.6317, 24., 52.3428, 120., 287.885, 720}
    
    


ParallelFunctionToList[ ] also provides a simplified way to perform this form of parallelism.
Operations with Non-Trivial Communication
Matrix Operations
In some embodiments, one or more functions can help solve matrix calculations in parallel:

    
    
        In[15]:=a=Table[i+3* $IdProc+2 j, {i, 2}, {j,4}]
        Out[15]:={{3, 5, 7, 9}, {4, 6, 8, 10}}
        In[16]:=t=ParallelTranspose[a]
        Out [16]: {{3, 4, 6, 7}, {5, 6, 8, 9}}

Fourier Transforms

    
    


A Fourier transform of a large array can be solved faster in parallel, or made possible on a cluster because it can all be held in memory. A two-dimensional Fourier transform of the above example follows:

    
    
        In[17]:=f=ParallelFourier[a]
        Out[17]:={{32.+0. I, −4. −4. I, −4., −4. +4. I}, {−3. −3. I, 0. +0. I, 0., 0. +0. I}}

Edge Cell Management

    
    


Many problems require interactions between partitions, but only on the edge elements. Maintaining these edges can be performed using EdgeCell[ ].

    
    
        In[18]:=a={2, 4, 5, 6, 7}+8*$IdProc
        Out[18]:={2, 4, 5, 6, 7}
        In[19]:=EdgeCell[a]; a
        Out[19]:={14, 4, 5, 6, 12}

Element Management

    
    


In particle-based problems, items can drift through space, sometimes outside the partition of a particular processor. This can be solved with ElementManage[1:

    
    
        In[20]:=list={{0,4},{1,3},{1,4},{0,5}}; fcn[x_]:=x[[1]]
        In[21]:=ElementManage[list, fcn]
        Out[21]:={{0, 4}, {0, 5}, {0, 4}, {0, 5}}
        In[21]:=ElementManage[list, 2]
        Out[21]:={{0, 4}, {0, 5}, {0, 4}, {0, 5}}
    
    


The second argument of ElementManage describes how to test elements of a list. The fcn identifier returns which processor is the “home” of that element. Passing an integer assumes that each element is itself a list, whose first element is a number ranging from 0 to the passed argument.
While the examples above involve Mathematica software and specific embodiments of MPI calls and cluster commands, it is recognized that these embodiments are used only to illustrate features of various embodiments of the systems and methods.
VI. Additional Embodiments
Although cluster computing techniques, modules, calls, and functions are disclosed with reference to certain embodiments, the disclosure is not intended to be limited thereby. Rather, a skilled artisan will recognize from the disclosure herein a wide number of alternatives for the exact selection of cluster calls, functions, and management systems. For example, single-node kernels can be managed using a variety of management tools and/or can be managed manually by a user, as described herein. As another example, a cluster node module can contain additional calls and procedures, including calls and procedures unrelated to cluster computing, that are not disclosed herein.
Other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. Moreover, the described embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein can be embodied in a variety of other forms without departing from the spirit thereof. Accordingly, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Thus, the present disclosure is not intended to be limited by the disclosed embodiments, but is to be defined by reference to the appended claims. The accompanying claims and their equivalents are intended to cover forms or modifications as would fall within the scope and spirit of the inventions.

## Claims

1. A computer cluster comprising:
a first processor;
a second processor;
a third processor;
at least one computer-readable medium in communication at least one of the first processor, the second processor, or the third processor;
a first kernel residing in the at least one computer-readable medium, said first kernel configured to translate commands into code for execution on the first processor;
a first cluster node module residing in the at least one computer-readable medium, said first cluster node module configured to send commands to the first kernel and receives commands from a user interface;
a second kernel residing in the at least one computer-readable medium, said second kernel configured to translate commands into code for execution on the second processor;
a second cluster node module residing in the at least one computer-readable medium, said second cluster node module configured to send commands to the second kernel and communicates with the first cluster node module;
a third kernel residing in the at least one computer-readable medium, said third kernel configured to translate commands into code for execution on the third processor; and
a third cluster node module residing in the at least one computer-readable medium, said third cluster node module configured to send commands to the third kernel and configured to communicate with the first cluster node module and the second cluster node module;
wherein the first cluster node module comprises a data structure in which messages originating from the second and third cluster node modules are stored.

2. The computer cluster of claim 1, wherein each of the first kernel, the second kernel, and the third kernel comprises a Mathematica kernel.

3. The computer cluster of claim 1, wherein each of the first cluster node module, the second cluster node module, and the third cluster node module comprises program code for implementing automatic load balancing on the first processor, the second processor, and the third processor.

4. The computer cluster of claim 1, further comprising a communications network for connecting at least two of the first processor, the second processor, or the third processor to one another.

5. The computer cluster of claim 1, wherein the at least one computer-readable medium comprises a first computer-readable medium coupled to at least the first processor and a second computer-readable medium coupled to at least the second processor, wherein the first kernel and the first cluster node module reside in the first computer-readable medium, and wherein the second kernel and the second cluster node module reside in the second computer-readable medium.

6. The computer cluster of claim 1, further comprising a cluster configuration module that initializes at least one of the first cluster node module, the second cluster node module, or the third cluster node module.

7. The computer cluster of claim 1, wherein the second cluster node module communicates with the first cluster node module using commands that implement at least a portion of a Message-Passing Interface.

8. The computer cluster of claim 1, wherein the data structure of the first cluster node module comprises a received message queue.

9. The computer cluster of claim 8, wherein the first cluster node module further comprises a message receiving queue, in which data specifying the location to which the first cluster node module can expect to receive an expression and an identifier of a processor from which the expression is expected to be sent are stored.

10. The computer cluster of claim 1, wherein the second cluster node module further comprises a received message queue in which messages originating from the first and third cluster node modules are stored.

11. The computer cluster of claim 1, wherein the first processor and the second processor reside in the same computer system.

12. The computer cluster of claim 1, wherein the first processor and the second processor reside on the same die.

13. The computer cluster of claim 1, wherein the first cluster node module comprises an advanced functions module, and wherein the advanced functions module comprises a call that evaluates an expression across the computer cluster in parallel.

14. The computer cluster of claim 13, wherein the advanced functions module comprises a call that calculates a Fourier transform across the computer cluster in parallel.

15. The computer cluster of claim 13, wherein the advanced functions module comprises one or more calls that implement guard-cell operations.

16. The computer cluster of claim 13, wherein the advanced functions module comprises one or more calls that evaluate matrix operations across the computer cluster in parallel.

17. A computer cluster comprising:
a plurality of nodes, wherein each node is configured to access a computer-readable medium comprising program code for a user interface and program code for a single-node kernel module configured to interpret user instructions;
a plurality of cluster node modules, wherein each cluster node module is configured to communicate with a single-node kernel and with one or more other cluster node modules, to accept instructions from the user interface, and to interpret at least some of the user instructions such that the plurality of cluster node modules communicate with one another in order to act as a cluster; and
a communications network to connect the nodes;
wherein one of the plurality of cluster node modules returns a result to the user interface.

18. The computer cluster of claim 17, wherein at least one of the plurality of cluster node modules comprises program code for storing data to one or more storage disks.

19. The computer cluster of claim 18, wherein the at least one of the plurality of cluster node modules further comprises program code for retrieving stored data from one or more storage disks.

20. The computer cluster of claim 17, wherein at least one of the plurality of cluster node modules comprises program code for collecting data from the plurality of cluster node modules and writing the data to a storage device associated with a single computer system.

21. The computer cluster of claim 17, wherein at least one of the plurality of cluster node modules comprises program code for reading data from a storage device associated with a single computer system and distributing the data to the plurality of cluster node modules within the computer cluster.

22. The computer cluster of claim 17, wherein at least one of the plurality of cluster node modules comprises program code for writing temporary data to a storage device associated with the same computer system on which the respective cluster node module is running.

23. The computer cluster of claim 17, wherein the communications network comprises at least one of a local bus, a local-area network, a wide-area network, an Ethernet network, a Token Ring network, a Frame Relay network, a Fiber Distributed Datalink Interface network, or an Asynchronous Transfer Mode network.

24. The computer cluster of claim 17, wherein the user interface comprises a Mathematica front end.

25. The computer cluster of claim 17, wherein the user interface comprises a command line.

26. The computer cluster of claim 17, wherein each of the plurality of cluster node modules comprises a toolkit comprising library calls that implement at least a portion of a Message-Passing Interface.

27. The computer cluster of claim 17, wherein each of the plurality of cluster node modules comprises a toolkit comprising one or more high-level cluster computing commands.

28. The computer cluster of claim 17, wherein the cluster computer system comprises at least one of a plurality of Macintosh® computers, a plurality of Windows®-based computers, or a plurality of computers running a Unix or Linux operating system.

29. A method of evaluating a command on a computer cluster comprising:
communicating a command from at least one of a user interface or a script to one or more cluster node modules within the computer cluster;
for each of the one or more cluster node modules, communicating a message based on the command to a respective kernel module associated with the cluster node module;
for each of the one or more cluster node modules, receiving a result from the respective kernel module associated with the cluster node module; and
for at least one of the one or more cluster node modules, responding to messages from other cluster node modules.

30. The method of claim 29, wherein communicating a message based on the command to a respective kernel module associated with the cluster node module comprises communicating a specially identified message to the respective kernel module.

31. The method of claim 29, further comprising, for at least one of the cluster node modules, forwarding the result to at least one of a user interface or a script running on a same computer system as the cluster node module.

32. The method of claim 29, further comprising, for at least one of the cluster node modules, communicating the result in a message to one or more other cluster node modules.

33. The method of claim 29, wherein responding to messages from other cluster node modules comprises:
forwarding messages from the other cluster node modules to a received message queue;
matching data from each entry in a message receiving queue with entries in the received message queue;
combining data from the message receiving queue with matching data in the received message queue; and
marking the matching data as completed.

34. The method of claim 29, wherein communicating a command from at least one of a user interface or a script to one or more cluster node modules within the computer cluster comprises communicating an instruction from a Mathematica Front End to a first cluster node module, wherein the first cluster node module forwards the instruction to other cluster node modules running on the computer cluster.

35. The method of claim 34, wherein the first cluster node module forwards the instruction to other cluster node modules running on the computer cluster using a command from a Message-Passing Interface.

36. The method of claim 29, wherein each of the one or more cluster node modules communicates with a respective kernel module using MathLink.

37. A computing system for executing Mathematica code on multiple nodes comprising:
a first node module in communication with a first Mathematica kernel executing on a first node;
a second node module in communication with a second Mathematica kernel executing on a second node; and
a third node module in communication with a third Mathematica kernel executing on a third node;
wherein the first node module, the second node module, and the third node module are configured to communicate with one another using a peer-to-peer architecture.

38. The computing system of claim 37, wherein each of the first node module, the second node module, and the third node module comprises:
a data structure for maintaining messages originating from other node modules; and
a data structure for maintaining data specifying:
a location to which a message is expected to be received; and
an identifier for a node from which the message is expected to be sent.