Patents by Inventor Vasant B. Rao

Vasant B. Rao has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 10360329
    Abstract: Embodiments relate to multi-cycle signal identification for static timing analysis. An aspect includes identifying, in a circuit under test, a multi-cycle signal, the multi-cycle signal having a longer period than a main clock signal of the circuit under test. Another aspect includes mapping a plurality of additional signals of the circuit under test onto the multi-cycle signal, the plurality of additional signals each having a shorter period than the multi-cycle signal. Yet another aspect includes performing static timing analysis of the circuit under test based on the multi-cycle signal.
    Type: Grant
    Filed: January 25, 2017
    Date of Patent: July 23, 2019
    Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
    Inventors: Robert J. Allen, Vasant B. Rao, William J. Wright, Xin Zhao
  • Patent number: 10325059
    Abstract: A method, system, and computer program product for performing incremental common path pessimism analysis in integrated circuit design includes performing common path pessimism removal (CPPR) analysis to provide timing credit for one or more paths that are subject to common path pessimism. The method also includes identifying one or more post-CPPR critical paths based on the CPPR analysis, setting flags for critical nodes of the one or more post-CPPR critical paths, performing a design fix to address the one or more post-CPPR critical paths, and applying a set of rules based on the design fix and the flags to identify seed points among the critical nodes of the one or more post-CPPR critical paths. Invalidating and re-performing the CPPR analysis is done only for paths associated with the seed points.
    Type: Grant
    Filed: October 27, 2017
    Date of Patent: June 18, 2019
    Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
    Inventors: Tsung-Wei Huang, Kerim Kalafala, Vasant B. Rao, Debjit Sinha, Natesan Venkateswaran
  • Publication number: 20190138916
    Abstract: Aspects include creating a knowledge base that identifies experts in a set of domains. Front-end processing is provided to an issue tracking system. The front-end processing includes receiving a report of an issue related to one of the domains, and accessing the knowledge base to locate an expert in the domain. The front-end processing also includes instructing the issue tracking system to route the received report of the issue to the located expert in the domain. The issue tracking system executes on a different processor than the front-end processing. Data collected from operation of the issue tracking system is monitored, and the knowledge base is updated based at least in part on the data collected from the operation of the issue tracking system.
    Type: Application
    Filed: November 9, 2017
    Publication date: May 9, 2019
    Inventors: Robert J. Allen, Adil Bhanji, Vasant B. Rao, Peter A. Twombly, Loma D. Vaishnav, Xin Zhao
  • Publication number: 20180046748
    Abstract: A method, system, and computer program product for performing incremental common path pessimism analysis in integrated circuit design includes performing common path pessimism removal (CPPR) analysis to provide timing credit for one or more paths that are subject to common path pessimism. The method also includes identifying one or more post-CPPR critical paths based on the CPPR analysis, setting flags for critical nodes of the one or more post-CPPR critical paths, performing a design fix to address the one or more post-CPPR critical paths, and applying a set of rules based on the design fix and the flags to identify seed points among the critical nodes of the one or more post-CPPR critical paths. Invalidating and re-performing the CPPR analysis is done only for paths associated with the seed points.
    Type: Application
    Filed: October 27, 2017
    Publication date: February 15, 2018
    Inventors: Tsung-Wei Huang, Kerim Kalafala, Vasant B. Rao, Debjit Sinha, Natesan Venkateswaran
  • Patent number: 9836572
    Abstract: A method, system, and computer program product for performing incremental common path pessimism analysis in integrated circuit design includes performing common path pessimism removal (CPPR) analysis to provide timing credit for one or more paths that are subject to common path pessimism. The method also includes identifying one or more post-CPPR critical paths based on the CPPR analysis, setting flags for critical nodes of the one or more post-CPPR critical paths, performing a design fix to address the one or more post-CPPR critical paths, and applying a set of rules based on the design fix and the flags to identify seed points among the critical nodes of the one or more post-CPPR critical paths. Invalidating and re-performing the CPPR analysis is done only for paths associated with the seed points.
    Type: Grant
    Filed: November 19, 2015
    Date of Patent: December 5, 2017
    Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
    Inventors: Tsung-Wei Huang, Kerim Kalafala, Vasant B. Rao, Debjit Sinha, Natesan Venkateswaran
  • Patent number: 9785737
    Abstract: A method, system, and computer program product to perform parallel multi-threaded common path pessimism removal in integrated circuit design include constructing, using a processor, a thread-specific graphical representation (TSGR) relating to each data node and clock node pair and performing processes in parallel for each TSGR. The processes include determining initial arrival times at the data node and the clock node, computing initial test slack based on the initial arrival times at the data node and the clock node, identifying fan-out nodes among the additional nodes, each fan-out node being an origin of at least two of the edges in the two or more paths to the clock node, generating one or more tags based the fan-out nodes, determining adjusted arrival times based on the one or more tags, and computing adjusted test slack based on the adjusted arrival times.
    Type: Grant
    Filed: November 17, 2015
    Date of Patent: October 10, 2017
    Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
    Inventors: David J. Hathaway, Kerim Kalafala, Vasant B. Rao, Alexander J. Suess, Vladimir Zolotov
  • Patent number: 9760665
    Abstract: An approach is provided in which an information handling system executes multiple timing constraint sensitivity tests on a circuit model using a first signal arrival time and generates multiple test results. The information handling system compares the multiple test results with a pre-determined probability threshold and, in response to determining that an amount of test failures included in the multiple test results meets a pre-determined failure probability threshold, the information handling system computes a timing constraint sensitivity of the circuit model based upon the first signal arrival time.
    Type: Grant
    Filed: August 22, 2015
    Date of Patent: September 12, 2017
    Assignee: International Business Machines Corporation
    Inventors: Sachin K. Gupta, Vasant B. Rao, Suriya T. Skariah, James E. Sundquist, James D. Warnock
  • Patent number: 9760664
    Abstract: An approach is provided in which an information handling system executes multiple timing constraint sensitivity tests on a circuit model using a first signal arrival time and generates multiple test results. The information handling system compares the multiple test results with a pre-determined probability threshold and, in response to determining that an amount of test failures included in the multiple test results meets a pre-determined failure probability threshold, the information handling system computes a timing constraint sensitivity of the circuit model based upon the first signal arrival time.
    Type: Grant
    Filed: July 7, 2015
    Date of Patent: September 12, 2017
    Assignee: International Business Machines Corporation
    Inventors: Sachin K. Gupta, Vasant B. Rao, Suriya T. Skariah, James E. Sundquist, James D. Warnock
  • Publication number: 20170206294
    Abstract: Embodiments relate to multi-cycle signal identification for static timing analysis. An aspect includes identifying, in a circuit under test, a multi-cycle signal, the multi-cycle signal having a longer period than a main clock signal of the circuit under test. Another aspect includes mapping a plurality of additional signals of the circuit under test onto the multi-cycle signal, the plurality of additional signals each having a shorter period than the multi-cycle signal. Yet another aspect includes performing static timing analysis of the circuit under test based on the multi-cycle signal.
    Type: Application
    Filed: January 25, 2017
    Publication date: July 20, 2017
    Inventors: Robert J. Allen, Vasant B. Rao, William J. Wright, Xin Zhao
  • Publication number: 20170147737
    Abstract: A method, system, and computer program product for performing incremental common path pessimism analysis in integrated circuit design includes performing common path pessimism removal (CPPR) analysis to provide timing credit for one or more paths that are subject to common path pessimism. The method also includes identifying one or more post-CPPR critical paths based on the CPPR analysis, setting flags for critical nodes of the one or more post-CPPR critical paths, performing a design fix to address the one or more post-CPPR critical paths, and applying a set of rules based on the design fix and the flags to identify seed points among the critical nodes of the one or more post-CPPR critical paths. Invalidating and re-performing the CPPR analysis is done only for paths associated with the seed points.
    Type: Application
    Filed: November 19, 2015
    Publication date: May 25, 2017
    Inventors: Tsung-Wei Huang, Kerim Kalafala, Vasant B. Rao, Debjit Sinha, Natesan Venkateswaran
  • Publication number: 20170140089
    Abstract: A method, system, and computer program product to perform parallel multi-threaded common path pessimism removal in integrated circuit design include constructing, using a processor, a thread-specific graphical representation (TSGR) relating to each data node and clock node pair and performing processes in parallel for each TSGR. The processes include determining initial arrival times at the data node and the clock node, computing initial test slack based on the initial arrival times at the data node and the clock node, identifying fan-out nodes among the additional nodes, each fan-out node being an origin of at least two of the edges in the two or more paths to the clock node, generating one or more tags based the fan-out nodes, determining adjusted arrival times based on the one or more tags, and computing adjusted test slack based on the adjusted arrival times.
    Type: Application
    Filed: November 17, 2015
    Publication date: May 18, 2017
    Inventors: David J. Hathaway, Kerim Kalafala, Vasant B. Rao, Alexander J. Suess, Vladimir Zolotov
  • Patent number: 9613171
    Abstract: Embodiments relate to multi-cycle signal identification for static timing analysis. An aspect includes identifying, in a circuit under test, a multi-cycle signal, the multi-cycle signal having a longer period than a main clock signal of the circuit under test. Another aspect includes mapping a plurality of additional signals of the circuit under test onto the multi-cycle signal, the plurality of additional signals each having a shorter period than the multi-cycle signal. Yet another aspect includes performing static timing analysis of the circuit under test based on the multi-cycle signal.
    Type: Grant
    Filed: January 15, 2016
    Date of Patent: April 4, 2017
    Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
    Inventors: Robert J. Allen, Vasant B. Rao, William J. Wright, Xin Zhao
  • Publication number: 20170011154
    Abstract: An approach is provided in which an information handling system executes multiple timing constraint sensitivity tests on a circuit model using a first signal arrival time and generates multiple test results. The information handling system compares the multiple test results with a pre-determined probability threshold and, in response to determining that an amount of test failures included in the multiple test results meets a pre-determined failure probability threshold, the information handling system computes a timing constraint sensitivity of the circuit model based upon the first signal arrival time.
    Type: Application
    Filed: July 7, 2015
    Publication date: January 12, 2017
    Inventors: SACHIN K. GUPTA, VASANT B. RAO, SURIYA T. SKARIAH, JAMES E. SUNDQUIST, JAMES D. WARNOCK
  • Publication number: 20170011153
    Abstract: An approach is provided in which an information handling system executes multiple timing constraint sensitivity tests on a circuit model using a first signal arrival time and generates multiple test results. The information handling system compares the multiple test results with a pre-determined probability threshold and, in response to determining that an amount of test failures included in the multiple test results meets a pre-determined failure probability threshold, the information handling system computes a timing constraint sensitivity of the circuit model based upon the first signal arrival time.
    Type: Application
    Filed: August 22, 2015
    Publication date: January 12, 2017
    Inventors: SACHIN K. GUPTA, VASANT B. RAO, SURIYA T. SKARIAH, JAMES E. SUNDQUIST, JAMES D. WARNOCK
  • Publication number: 20160364519
    Abstract: Examples of techniques for analyzing and generating timing reports for circuits are described herein. A computer-implemented method includes splitting a netlist or cross section of a circuit into sub-circuits. The method further includes building a timing graph by combining generated timing models of the sub-circuits. The method includes determining a full set of dependencies based on each sub-circuit's dependent configuration parameters. The method also further includes generating a sample plan for each sub-circuit. The method includes receiving results from a simulation for each sub-circuit based on the sample plan for each sub-circuit. The method includes generating algebraic forms for an early delay, a late delay, and a slew by curve fitting across the configuration parameters. The method includes propagating arrival times and slew in algebraic forms throughout the timing graph. The method includes evaluating checks based on selected projections from the timing graph to find a worst slack configuration.
    Type: Application
    Filed: June 11, 2015
    Publication date: December 15, 2016
    Inventors: Robert J. Allen, Yanai Danan, Vasant B. Rao, Xin Zhao
  • Patent number: 9501608
    Abstract: Examples of techniques for analyzing and generating timing reports for circuits are described herein. A computer-implemented method includes splitting a netlist or cross section of a circuit into sub-circuits. The method further includes building a timing graph by combining generated timing models of the sub-circuits. The method includes determining a full set of dependencies based on each sub-circuit's dependent configuration parameters. The method also further includes generating a sample plan for each sub-circuit. The method includes receiving results from a simulation for each sub-circuit based on the sample plan for each sub-circuit. The method includes generating algebraic forms for an early delay, a late delay, and a slew by curve fitting across the configuration parameters. The method includes propagating arrival times and slew in algebraic forms throughout the timing graph. The method includes evaluating checks based on selected projections from the timing graph to find a worst slack configuration.
    Type: Grant
    Filed: June 11, 2015
    Date of Patent: November 22, 2016
    Assignee: International Business Machines Corporation
    Inventors: Robert J. Allen, Yanai Danan, Vasant B. Rao, Xin Zhao
  • Patent number: 7643981
    Abstract: The present invention provides for simulating signal transitions. Circuit characteristics are generated. Circuit characteristics are loaded into memory. Circuit behaviour is simulated. A non-leading edge circuit transition is captured. This occurs in software.
    Type: Grant
    Filed: July 22, 2004
    Date of Patent: January 5, 2010
    Assignee: International Business Machines Corporation
    Inventors: Sang Y. Lee, Vasant B. Rao, Jeffrey Soreff, James Warnock, David Winston
  • Patent number: 6763504
    Abstract: A method for further reducing RC parasitics in an interconnect network following internal node elimination is described. A resistor is initially selected as a candidate for shorting, and it is established whether the accumulated delay error at either end of the resistor is less than a predetermined threshold. This threshold must be a fraction of the time-constant threshold selected by internal node elimination techniques in order to limit the growth of the accumulated delay errors. An important aspect of the invention is the simplicity of the formula used to change the downstream resistor values, namely, the product of the value of the resistor shorted and the ratio of the cumulative downstream capacitances of the two ends of the resistor whose value is being changed. This particular choice of updating the downstream resistor values minimizes the absolute-value of the delay errors at every node due to shorting of the selected resistor.
    Type: Grant
    Filed: September 6, 2002
    Date of Patent: July 13, 2004
    Assignee: International Business Machines Corporation
    Inventors: Vasant B. Rao, Ravichander Ledalla, Jeffrey P. Soreff, Fred L. Yang
  • Publication number: 20040049746
    Abstract: A method for further reducing RC parasitics in an interconnect network following internal node elimination is described. A resistor is initially selected as a candidate for shorting, and it is established whether the accumulated delay error at either end of the resistor is less than a predetermined threshold. This threshold must be a fraction of the time-constant threshold selected by internal node elimination techniques in order to limit the growth of the accumulated delay errors. An important aspect of the invention is the simplicity of the formula used to change the downstream resistor values, namely, the product of the value of the resistor shorted and the ratio of the cumulative downstream capacitances of the two ends of the resistor whose value is being changed. This particular choice of updating the downstream resistor values minimizes the absolute-value of the delay errors at every node due to shorting of the selected resistor.
    Type: Application
    Filed: September 6, 2002
    Publication date: March 11, 2004
    Applicant: International Business Machine Corporation
    Inventors: Vasant B. Rao, Ravichander Ledalla, Jeffrey P. Soreff, Fred L. Yang
  • Publication number: 20030182639
    Abstract: A transistor-level simulator system and method which uses a simulator=s API=s construct a circuit code module which is used to perform circuit simulation of input and output wave forms without the user having to provide a detailed netlist. This circuit simulation tool may be used on more complex gates where other models may be impractical to obtain without loss in the fidelity of the waveforms.
    Type: Application
    Filed: March 25, 2002
    Publication date: September 25, 2003
    Applicant: International Business Machines Corporation
    Inventors: Timothy S. Lehner, Vasant B. Rao