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Any way to reduce the time it takes for transient to start on a very large design?

david1110

Virtuoso Version: ICADVM20.1-64b.500.27
Spectre Version: 21.1.0.484.isr11

I'm running post-layout transient simulations (with SpectreX) on a very large circuit (broken down into a few large DSPFs and nports) and each time I start a new one it takes around 2.5 hours before even starting the initial conditions calculation. Here are some of the big time stamps in spectre.out:

...

Time for Elaboration: CPU = 1.60081 ks (26m  40.8s), elapsed = 1.60084 ks (26m  40.8s).
Time accumulated: CPU = 2.0675 ks (34m  27.5s), elapsed = 2.06818 ks (34m  28.2s).
Peak resident memory used = 52.6 Gbytes.

...

Time for EDB Visiting: CPU = 2.14149 ks (35m  41.5s), elapsed = 2.14123 ks (35m  41.2s).
Time accumulated: CPU = 4.20899 ks (1h 10m 9s), elapsed = 4.20941 ks (1h 10m 9s).
Peak resident memory used = 77.8 Gbytes.

...

Time for parsing: CPU = 9.2601 ks (2h 34m 20s), elapsed = 5.04084 ks (1h 24m 1s).
Time accumulated: CPU = 13.4691 ks (3h 44m 29s), elapsed = 9.25025 ks (2h 34m 10s).
Peak resident memory used = 122 Gbytes.

Obviously, with a very large circuit I expect it to take time, but does it need to take this long every time I run it on the same circuit (while changing some variables, e.g. clock phases, biases, etc)? Is there any way to reuse the results of e.g. "Elaboration" and "EDB Visiting" and "parsing" from the last time I ran it, similar to how I can reuse initial conditions?

  • I would strongly advise you to contact customer support. There's some detailed diagnostics that could be performed to help determine where it might be spending the time, but this is something that needs support/R&D involvement. I'd also recommend you try the latest SPECTRE 23.1 ISR too just in case it's an issue that's been resolved (the version you're using is 17 months old, so there will have been a number of fixes in that time).

    Regards,

    Andrew

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