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Multithreading not working

Rob Gregoire

I'm simulating a 15 stage SAR ADC and even though the output log indicates that 4 processors are used with multi-threading I am not getting a reduction in Elapsed Time compared to CPU time. I even tried it with a couple ADCs in parallel to make sure the ADC is big enough but I still get no improvement.

It seems to be related to the process design kit. I can simulate a similar ADC in another process and get speed improvement. I'm using IC 6. Any ideas on what to check or what would be helpful in debugging? My internet search only turned up a question from 2006 that indicated that it doesn't work with some CMOS models.

Parents

  • Thanks for your response. To answer you questions:

    MMSIM131. I am already. defining number of threads under simulations->Options->Analog (turning multithreading on, nthreads=4)

    Some more information (red emphasis mine):  Using IC6.1.5

    Right before the transient analysis is listed in the output log there is a notice stating:

    Notice from spectre during initial setup.
        Multithreading Enabled: 4 threads on system with 24 available processors.
            
        58 notices suppressed.


    Time for parsing: CPU = 173.973 ms, elapsed = 266.827 ms.
    Time accumulated: CPU = 2.12368 s, elapsed = 2.34084 s.
    Peak resident memory used = 96.9 Mbytes.

    Entering remote command mode using MPSC service (spectre, ipi, v0.0, spectre0_10789_18, ).

    ============================================================

    And at the end of the simulation:

        tran: time = 410.9 ns    (99.6 %), step = 3.464 ps     (840 u%)
        tran: time = 411.1 ns    (99.7 %), step = 1.216 ps     (295 u%)
        tran: time = 411.4 ns    (99.7 %), step = 979.1 fs     (237 u%)
    Number of accepted tran steps =             124642

    Notice from spectre during transient analysis `tran'.
        Trapezoidal ringing is detected during tran analysis.
            Please use method=trap for better results and performance.

    Initial condition solution time: CPU = 4.46432 s, elapsed = 4.46464 s.
    Intrinsic tran analysis time:    CPU = 11.3365 ks, elapsed = 11.3387 ks.
    Total time required for tran analysis `tran': CPU = 11.341 ks (3h 9m 1s), elapsed = 11.3433 ks (3h 9m 3s).
    Time accumulated: CPU = 11.3436 ks (3h 9m 4s), elapsed = 11.3462 ks (3h 9m 6s).
    Peak resident memory used = 372 Mbytes.

    Any help would be appreciated. This is the first time my team has run into this one. Again, if I run a similar design in another process I do get a reduction in elapsed time vs CPU time (and the elapsed time is correct).

    --rg

Reply

  • Thanks for your response. To answer you questions:

    MMSIM131. I am already. defining number of threads under simulations->Options->Analog (turning multithreading on, nthreads=4)

    Some more information (red emphasis mine):  Using IC6.1.5

    Right before the transient analysis is listed in the output log there is a notice stating:

    Notice from spectre during initial setup.
        Multithreading Enabled: 4 threads on system with 24 available processors.
            
        58 notices suppressed.


    Time for parsing: CPU = 173.973 ms, elapsed = 266.827 ms.
    Time accumulated: CPU = 2.12368 s, elapsed = 2.34084 s.
    Peak resident memory used = 96.9 Mbytes.

    Entering remote command mode using MPSC service (spectre, ipi, v0.0, spectre0_10789_18, ).

    ============================================================

    And at the end of the simulation:

        tran: time = 410.9 ns    (99.6 %), step = 3.464 ps     (840 u%)
        tran: time = 411.1 ns    (99.7 %), step = 1.216 ps     (295 u%)
        tran: time = 411.4 ns    (99.7 %), step = 979.1 fs     (237 u%)
    Number of accepted tran steps =             124642

    Notice from spectre during transient analysis `tran'.
        Trapezoidal ringing is detected during tran analysis.
            Please use method=trap for better results and performance.

    Initial condition solution time: CPU = 4.46432 s, elapsed = 4.46464 s.
    Intrinsic tran analysis time:    CPU = 11.3365 ks, elapsed = 11.3387 ks.
    Total time required for tran analysis `tran': CPU = 11.341 ks (3h 9m 1s), elapsed = 11.3433 ks (3h 9m 3s).
    Time accumulated: CPU = 11.3436 ks (3h 9m 4s), elapsed = 11.3462 ks (3h 9m 6s).
    Peak resident memory used = 372 Mbytes.

    Any help would be appreciated. This is the first time my team has run into this one. Again, if I run a similar design in another process I do get a reduction in elapsed time vs CPU time (and the elapsed time is correct).

    --rg

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