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Simulators >> Circuit Simulators >> Convergence issue when vpwlf is used
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Message started by schehrazi on May 1^st, 2009, 6:15pm

Title: Convergence issue when vpwlf is used
Post by schehrazi on May 1^st, 2009, 6:15pm

Hi,

Has anybody faced convergence issues in transient simulation when a vpwlf source is present in the circuit?

In my case, the simulation goes smoothly with sinusoidal sources but once an arbitrary signal is used, if the output format is SST2, I get "SST2 Error: Invalid control value" and the simulation terminates.

I changed the output format to psf using

envSetVal("spectre.envOpts" "simOutputFormat" 'string "psfbin")

This time the simulation does not terminate but I get a lot of "zero diagonal found in jacobian" warnings and eventually, the simulation terminates before it is finished.

Any hit to fix this? I am using icfb 5141.

Thanks in advance.

*

Title: Re: Convergence issue when vpwlf is used
Post by schehrazi on May 12^th, 2009, 10:57am

Hi everyone,

My problem was resolved by disabling the "multithreading" option of Spectre. Spectre is supposed to automatically disable that option if the count of BSIM devices is less than 250 which it does not.

In my case, using multithreading cost me much more time that it could save me. The simulation rarely converged, it was time and machine dependent. At some point, I could not believe what I was seeing because the same ocean code ran on one machien successfully and failed when tried on another machine.

Avoid multithreading if you have less than 250 BSIM devices!