Patent Publication Number: US-8972913-B1

Title: Concurrent multiparameter simulation system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/694,705, filed Aug. 29, 2012, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of Art 
     The disclosure generally relates to the field of electrical circuit simulations, and more specifically to concurrent, multi-parameter analysis of electrical circuits. 
     2. Description of the Related Art 
     As the complexity of electrical and electronic circuits increase, the tools used for their simulation also increase in complexity. Furthermore, due to the complexity of the simulations, and to increase the simulation speed, current analysis tools specialize in one aspect of the electrical circuit while considering other aspects of the electrical circuit as being constant. For instance, a timing analysis tool may be able to determine the delay of the different components of the electrical circuit but the timing analysis tool may consider some parameters that affect timing, such as the temperature of the electrical circuit to be constant. This reduces the accuracy of the analysis tools since parameters that are considered to be constant may actually be changing with the operation of the electrical circuit. 
     To simulate multiple parameters of the electrical circuit, users may use multiple analysis tools, each simulating one parameter of the electrical circuit. For instance, a user may use a voltage analysis tool, as well as a thermal analysis tool to simulate the voltage at different nodes of the electrical circuit and the temperature profile of the electrical circuit. Since every parameter is analyzed independently to each other, analyzing the temperature profile of the electrical circuit does not necessarily improve the accuracy of the voltage simulation. 
     SUMMARY 
     Embodiments of the invention present a new way for concurrently simulating multiple operating parameters of a design of an electrical circuit. The simulation system includes multiple analysis engines, each simulation engine capable of simulating one parameter of the electrical circuit. The simulation system determines a first simulation time for which to perform the analysis of the design. The simulation system also determines a first set of environmental parameters for the design. Each of the analysis engines simulates the design based on the first set of environmental parameters. Based on the results from each of the analysis engines, the first set of environmental parameters is updated. 
     A determination is made whether the simulation results have converged. If the simulation results have not converged, each of the analysis engines simulates the design using the updated set of environmental parameters representing simulation of the same simulation time. Otherwise, if the simulation results are determined to be convergent, the simulation system determines a second simulation time and repeats the simulation process for a second simulation time. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The disclosed embodiments have other advantages and features which will be more readily apparent from the detailed description, the appended claims, and the accompanying figures (or drawings). A brief introduction of the figures is below. 
         FIG. 1  illustrates one embodiment of components of an example machine able to read instructions from a machine-readable medium and execute them in a processor. 
         FIG. 2A  illustrates a conventional simulation system for simulating multiple operating parameters of an electrical circuit. 
         FIG. 2B  illustrates a simulation system for concurrently simulating multiple operating parameters of an electrical circuit, according to one embodiment. 
         FIG. 3A  illustrates a flow diagram for simulating multiple operating parameters. 
         FIG. 3B  illustrates a flow diagram for simulating a single operating parameter. 
         FIG. 4  illustrates a flow diagram for concurrently simulating multiple operating parameters of an electrical circuit, according to one embodiment. 
         FIG. 5  illustrates a timing diagram of a simulation according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The Figures (FIGS.) and the following description relate to preferred embodiments by way of illustration only. It should be noted that from the following discussion, alternative embodiments of the structures and methods disclosed herein will be readily recognized as viable alternatives that may be employed without departing from the principles of what is claimed. 
     Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying figures. It is noted that wherever practicable similar or like reference numbers may be used in the figures and may indicate similar or like functionality. The figures depict embodiments of the disclosed system (or method) for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles described herein. 
     Computing Machine Architecture 
     FIG. ( FIG. 1  is a block diagram illustrating components of an example machine able to read instructions from a machine-readable medium and execute them in a processor (or controller). Specifically,  FIG. 1  shows a diagrammatic representation of a machine in the example form of a computer system  100  within which instructions  124  (e.g., software) for causing the machine to perform any one or more of the methodologies discussed herein may be executed. In alternative embodiments, the machine operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. 
     The machine may be a server computer, a client computer, a personal computer (PC), a tablet PC, a personal digital assistant (PDA), a cellular telephone, a smartphone, or any machine capable of executing instructions  124  (sequential or otherwise) that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include any collection of machines that individually or jointly execute instructions  124  to perform any one or more of the methodologies discussed herein. 
     The example computer system  100  includes a processor  102  (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), one or more application specific integrated circuits (ASICs), one or more radio-frequency integrated circuits (RFICs), or any combination of these), a main memory  104 , and a static memory  106 , which are configured to communicate with each other via a bus  108 . The computer system  100  may further include graphics display unit  110  (e.g., a plasma display panel (PDP), a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)). The computer system  100  may also include alphanumeric input device  112  (e.g., a keyboard), a cursor control device  114  (e.g., a mouse, a trackball, a joystick, a motion sensor, or other pointing instrument), a storage unit  116 , a signal generation device  118  (e.g., a speaker), and a network interface device  820 , which also are configured to communicate via the bus  108 . 
     The storage unit  116  includes a machine-readable medium  122  on which is stored instructions  124  (e.g., software) embodying any one or more of the methodologies or functions described herein. The instructions  124  (e.g., software) may also reside, completely or at least partially, within the main memory  104  or within the processor  102  (e.g., within a processor&#39;s cache memory) during execution thereof by the computer system  100 , the main memory  104  and the processor  102  also constituting machine-readable media. The instructions  124  (e.g., software) may be transmitted or received over a network  126  via the network interface device  120 . 
     While machine-readable medium  122  is shown in an example embodiment to be a single medium, the term “machine-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store instructions (e.g., instructions  124 ). The term “machine-readable medium” shall also be taken to include any medium that is capable of storing instructions (e.g., instructions  124 ) for execution by the machine and that cause the machine to perform any one or more of the methodologies disclosed herein. The term “machine-readable medium” includes, but not be limited to, data repositories in the form of solid-state memories, optical media, and magnetic media. 
     Electrical Circuit Analysis Architecture 
       FIG. 2A  illustrates a conventional simulation system  201 A for simulating multiple operating parameters. The simulation system  201 A receives a simulation design and a set of environmental parameters, and outputs a simulation result. Simulation System  201  includes analysis engine  210 A, analysis engine  210 B, analysis engine  210 C, and analysis engine  210 D. For illustration purposes,  FIG. 2A  contains four analysis engines, but it could contain more analysis engines or less analysis engines depending on the number of operating parameters to be simulated. 
     Each analysis engine calculates one operating parameter for the simulation design. For example, an analysis engine may perform timing analysis, power analysis, voltage/current analysis, temperature analysis, parasitic RLC analysis, etc. The analysis engines  210  calculate their respective simulation parameters based on a set of environmental parameters. 
     As used herein, environmental parameters of an analysis engine are a set of parameters that are not computed by the analysis engine as part of the simulation. The environmental parameters may, for example, be provided to the analysis engine as an input by the user running a simulation or by a simulation engine invoking the analysis engine. For a given analysis engine, during the simulation of a design, the environmental parameters are kept constant, while the simulation parameters are being computed. For instance, for a thermal analysis engine, the timing, voltage, current, and power of a circuit design may be kept constant while computing the temperature profile throughout the circuit. Thus, for the thermal analysis engine, the timing, voltage, current, and power are environmental parameters. 
     The analysis engines  210  of  FIG. 2A  compute their respective operating parameters sequentially and the output of an analysis engine is used as an input to the next analysis engine. For instance, the first analysis engine  210 A (e.g., timing analysis) computes a first operating parameter (e.g., timing) assuming the environmental parameters (e.g., voltage, current, temperature profile, etc.) to be constant. After the first analysis engine  210 A finished computing the first operating parameter, the second analysis engine  210 B (e.g., temperature analysis) computes a second operating parameter (e.g., temperature) based on the results from the first analysis engine  210 A. The results from the first analysis engine  210 A and the second analysis engine  210 B are used as an input to the third analysis engine  210 C. This process is repeated until every analysis engine  210  has finished computing its respective operating parameter. 
     Even though analysis engines  210  compute their respective simulation parameters assuming their environmental parameters being constant, in reality the environmental parameters may not be constant. For example, as current passes though an electrical circuit, the temperature of the different components of the electrical circuit may increase. As a result, the properties of those components (e.g., electron/hole mobility, electron/hole free mean path, resistivity of a metal layer) may also change. Since analysis engines that have temperature profile as an environmental parameter (e.g., timing analysis engine, power analysis engine, etc.) do not take into consideration the change in temperature as the circuit is being operated, the simulation results obtained from those analysis engines may not be accurate. 
       FIG. 5  illustrates a timing diagram of a simulation. Each simulation may be performed for a first time interval T 1  (e.g., 10 ms). That is, the electrical circuit is simulated for an operating time of T 1 . To simulate the behavior of the electrical circuit, the first time interval T 1  is divided into multiple sub-time intervals t 0 , t 1 , t 2 , . . . , t z , separated by Δt (e.g., 1 μs). In some analysis engines, Δt may be constant throughout the entire simulation. In other analysis engines, Δt may change depending on different factors (e.g., precision needed by user, convergence of simulation). 
     Even though  FIG. 5  is described in terms of simulation times, a simulation does not have to be perform as a function of time. As used herein, a simulation time is any parameter that is varied (or swept) during the simulation to determine the behavior of the electrical circuit as a function of varying parameter. For instance a simulation may be performed as a function of the supply voltage (e.g., supply voltage ranging from 1V to 5V). Here, the first simulation time refers to the first supply voltage simulated (e.g., 1V), the last simulation time refers to the last supply voltage simulated (e.g., 5V), and Δt refers to a voltage step (e.g., 0.1V) used to sweep the supply voltage from the first voltage level (1V) to the last voltage level (5V). 
       FIG. 3A  illustrates a flow diagram for simulating multiple operating parameters by a conventional simulation system  201 A. The first analysis engine  210 A receives  301  the design to be simulated and  311  a set of environmental parameters. In some embodiments, one or more environmental parameters may be received from a user using the simulation system  201 A. In other embodiments, a default value may be used for environmental parameters that are not received. The first analysis engine  210 A simulates  313  the design starting from the first simulation time t 0  until the last simulation time t z  of  FIG. 5 , and sends the results of the simulation to the second simulation engine. 
     The second analysis engine  210 B receives  301  the design to be simulated. Additionally, the second analysis engine  210 B receives  321  the simulation results from the first analysis engine and the environmental parameters previously received by the first analysis engine. In some embodiments, the first analysis engine  210 A updates the environmental parameters to include the results of the first analysis and sends the updated environmental parameters to the second analysis engine. The second simulation engine  210 B simulates  323  the design starting again from the first simulation time t 0  and ending at the last simulation time t z  of  FIG. 5 . The second analysis engine and sends  325  the results of the design and the environmental parameters to the third analysis engine  210 C. 
     This process is repeated for every analysis engine  210  used by the simulation system  201 A. After the last analysis engine (e.g., fourth simulation engine  210 D) received  341  the set of environmental parameters, the last parameter is simulated  343  and the simulation results is outputted  345 . 
       FIG. 3B  illustrates a flow diagram for simulating one operating parameter by an analysis engine  210 . The analysis engine  210  determines  351  the first simulation time (t 0  of  FIG. 5 ). The simulation engine  210  simulates  353  the design for the determined first simulation time t 0 . After the simulation of the design for t 0  has been completed, the analysis engine determines  355  whether every simulation time has been simulated. If there are more simulation times to simulate, the analysis engine  210  determines  357  the next simulation time (e.g., t 1  of  FIG. 5 ) and simulates the design for the determined next simulation time. This process is repeated until every simulation time has been simulated. 
     One problem with the simulation flow of simulation system  201 A is that the second operating parameter is computed based on the results from the first analysis engine  210 A, but the results of the first analysis engine  210 A were calculated assuming the second operating parameter being constant. As the second analysis engine  210 B computes the second operating parameter, the values of the first parameter calculated by the first analysis engine  210 A becomes invalid, reducing the accuracy of the simulation results of the simulation system  201 A. 
     Concurrent Analysis of Multiple Parameters 
       FIG. 2B  illustrates a simulation system  201 B for concurrently simulating multiple parameters of an electrical circuit, according to one embodiment. Simulation system  201 B includes analysis engine  220 A, analysis engine  220 B, analysis engine  220 C, and analysis engine  220 D. For illustration purposes,  FIG. 2B  contains four analysis engines, but it could contain more analysis engines or less analysis engines depending on the number of operating parameters to be simulated. 
     Each analysis engine  220  computes its respective operating parameter and updates the environmental parameters of other analysis engines  220  accordingly. For instance, a thermal analysis engine  220  may compute the temperature profile within an electrical circuit and updates other analysis engines (e.g., timing analysis engine, power analysis engine, etc.) of the changes in temperature throughout the electrical circuit. Every analysis engine  220  performs its respective analysis of the electrical circuit concurrently. That is, before the next simulation time t n+1  is analyzed, every operating parameter of the electrical circuit for the current simulation time t n  is calculated. When every operating parameter for the current simulation time t n  has been calculated, the environmental parameters for every analysis engine are updated and the operating parameters for the next simulation time t n+1  are calculated. 
     The simulation system  201 B beneficially improves the accuracy of the simulation results since environmental parameters are updated while each analysis engine is calculating their respective operating parameters of the simulated design. 
       FIG. 4  illustrates a flow diagram for concurrently simulating multiple operating parameters by a simulation system  210 B, according to one embodiment. The simulation system  210 B receives  401  the design to be simulated. The simulation system  210 B determines  403  an initial value for the environmental parameters. In one embodiment, the simulation system  210 B determines the initial value for the environmental parameters based on an initial value of each of the operation parameters determined by each simulation engine  220 . Each analysis engine  220  may determine an initial value of their respective operating parameter based on an initial guess of the environmental parameters. 
     The simulation system  201 B determines the first simulation time (e.g., t 0  of  FIG. 5 ). Each simulation engine determines a first value of their respective operating parameters. That is, if four analysis engines  220 A,  220 B,  220 C, and  220 D are used to analyze the design, the first analysis engine  220 A analyzes  407  the received design to determine a first value of the first operating parameter, the second analysis engine  220 B analyzes  409  the received design to determine a first value of the second operating parameter, the third analysis engine  220 C analyzes  411  the design to determine a first value of the third operating parameter, and the fourth analysis engine  220 D analyzes  413  the design to determine a first value of the fourth operating parameter. 
     The simulation system  201 B updates  415  the set of environmental parameters based on the results of each of the analysis engines and determines  417  whether the simulation results converged. If the simulation results did not converge, each of the analysis engines repeat the analysis of the design for the same simulation time using the updated set of environmental parameters. This process is repeated until the simulation system determines that the simulation results for every analysis engine  220  have converged. 
     As used herein, a simulation result is determined to be convergent if the result from the current analysis is within a threshold value of the results of the previous analysis for the same simulation time. For example, a thermal analysis engine may perform a first analysis of a design, for a given simulation time (t n ), and determine that the temperature of a component is 35.00° C. Then, for the same simulation time (t n ), the thermal analysis engine may perform a second analysis and determine that the temperature of the component is 35.10° C. If the convergence threshold is set at 0.05° C., then the simulation results of the thermal analysis engine is not convergent. The thermal analysis engine can then perform a third analysis of the design and determine that the temperature of the component is 35.07° C. Since the difference between the second simulation result (35.10° C.) and the third simulation result (35.07° C.) is less than the convergence threshold (0.05° C.), then the simulation results for the thermal analysis engine are considered to be convergent for the current simulation time (t n ). In some embodiments, the simulation results are only considered to be convergent if all simulation results from all the analysis engines  220  are convergent. 
     After the simulation results for the current simulation time have converged, the simulation system  201 B determines  419  whether every simulation time has been simulated. If every simulation time has been simulated, then the simulation of the received design ends. Otherwise, if there are more simulation times to be simulated, the simulation system  201 B determines  421  the next simulation times and repeats the simulation process for the next simulation time. 
     Since environmental parameters of analysis engines  220  that are simulated by an analysis engine  220  of simulation system  201 B are not kept constant, the accuracy of the simulation results of simulation system  201 B is improved compared to the simulation results of simulation system  201 A. 
     Additional Configuration Considerations 
     Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein. 
     Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium or in a transmission signal) or hardware modules. A hardware module is tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. In example embodiments, one or more computer systems (e.g., a standalone, client or server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein. 
     In various embodiments, a hardware module may be implemented mechanically or electronically. For example, a hardware module may comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations. 
     The various operations of example methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions. The modules referred to herein may, in some example embodiments, comprise processor-implemented modules. 
     The one or more processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., application program interfaces (APIs).) 
     The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the one or more processors or processor-implemented modules may be located in a single geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the one or more processors or processor-implemented modules may be distributed across a number of geographic locations. 
     Some portions of this specification are presented in terms of algorithms or symbolic representations of operations on data stored as bits or binary digital signals within a machine memory (e.g., a computer memory). These algorithms or symbolic representations are examples of techniques used by those of ordinary skill in the data processing arts to convey the substance of their work to others skilled in the art. As used herein, an “algorithm” is a self-consistent sequence of operations or similar processing leading to a desired result. In this context, algorithms and operations involve physical manipulation of physical quantities. Typically, but not necessarily, such quantities may take the form of electrical, magnetic, or optical signals capable of being stored, accessed, transferred, combined, compared, or otherwise manipulated by a machine. It is convenient at times, principally for reasons of common usage, to refer to such signals using words such as “data,” “content,” “bits,” “values,” “elements,” “symbols,” “characters,” “terms,” “numbers,” “numerals,” or the like. These words, however, are merely convenient labels and are to be associated with appropriate physical quantities. 
     Unless specifically stated otherwise, discussions herein using words such as “processing,” “computing,” “calculating,” “determining,” “presenting,” “displaying,” or the like may refer to actions or processes of a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or a combination thereof), registers, or other machine components that receive, store, transmit, or display information. 
     As used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. For example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise. 
     Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for a system and a process for concurrently simulating multiple parameters of an electrical circuit design through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims.