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ScreenSaver Science**  Summary:  ScreenSaver ScienceTM (SSS) is a distributed computing        paradigm where useful computations are performed on an organization's        computers whenever their screensavers are on. In contrast to other distributed computing projects, such as SETI@Home, the clients of this system, that is, the part that runs on the user's workstation, will not consist of a dedicated scientific application.  In the SSS system, the client will have no particular calculation embedded in it at all, but instead will be capable of performing any computation, subject to local resource constraints such as the amount of memory available.  This is made possible through the use of applications compiled to portable Java bytecode along with the Jini and JavaSpaces technologies that have been enabled by the Java environment. Another fundamental difference between SSS and other distributed computing projects is that SSS clients can communicate with each other during the computation in order to coordinate the computation, rather that simply exchanging data with a central job manager, thus presenting a distributed parallel computing model to the SSS application programmer.      Additional Technical Details:  An SSS installation consists of several loosely coupled processes. The core of the system consists of one or more instances of a JavaSpace.  These "spaces" are used to store tasks to be computed as well as results from these tasks and any other shared objects needed by the tasks or the SSS system itself.  The current system uses the JavaSpace provided by Sun Microsystems however this requirement can be fulfilled by any implementation of the JavaSpace specification. Other processes in the SSS system include monitors to view the state of the system as it operates, registration programs to enter users into the system, and other programs that inspect the spaces and add or remove objects as needed.  There are two types of participants in SSS: Servers, who compute SSS tasks on their machines while they would otherwise be idle, and Clients who submit tasks to be computed.  A person can participate as an SSS Server by registering with the SSS system. Registration consists of choosing a unique ID for themselves and each of the machines that will be running the SSS Server. They can then install the SSS Server on each of their machines.  There is actually no specific screen saver program used by SSS, it simply uses the same interface into the operating system that is used by the local screen saver program to control when the SSS Server runs and when it is killed.  Preferences can be given to direct your SSS Servers to run tasks submitted by specific SSS Clients if there are any available.  An SSS Client must also register, choosing a unique ID for themselves, before they can submit tasks into the system.  The computational model presented to the developer of SSS tasks is currently a subject of research. However, we are targeting large, highly parallel, scientific applications that can be divided into computational tasks that can fit on current typical PCs and scientific workstations. All tasks must consist of pure Java bytecode, typically written in Java,  so that they may run on any participating SSS Server. Communication between tasks is provided through the same JavaSpace that is used to hold the SSS objects.  Tasks have the same access to the JavaSpace as the other parts of the SSS system and so may generate additional tasks if needed, or delete unneeded tasks. This presents many possibilities to the SSS task programmer. For example, they may design a "manager" task for their computation that in turn submits some number of "worker" tasks and then resubmits itself back into the system before it exits, to be run again when more worker tasks are needed.  Programs can be run external to the SSS system that can also access the SSS JavaSpace to monitor and control the execution of tasks. Data structures shared between tasks can be kept in SSS JavaSpace.  A remote file service has been developed to provide SSS tasks access to large files for input and output.  Each file is represented by an object that is stored in the SSS JavaSpace and access to remote files is controlled through those objects. A simple API is used to open, read, write, and close remote files, using standard Java input and output streams.  Security will be provided to both SSS Servers and Clients, allowing for mutual identification and authentication, by technologies incorporated into the next release of Jini.      Applications:  *Quantum Monte Carlo Studies of Nitrated Organic Compounds*  The quantum Monte Carlo (QMC) method is a high accuracy ab initio method for predicting electronic properties of chemical systems. The QMC method is highly parallelizable and has relatively modest computational demands for large systems, compared to methods of similar accuracy. We are applying QMC to decomposition studies of methyl nitrates as well as nitrated cubane compounds. Problems of these sizes are of interest from practical and theoretical perspectives.     Return to High Performance Computing
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    Created December 6, 2010, Updated September 21, 2016
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