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c-thaler's avatar
c-thaler
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2 years ago

Questa simulation hangs (nondeterministic)

I run a Questa simulation for an IP core from the command line on a Linux server. Usually, the simulation finishs successfully. But every now and then the simulation hangs. When it hangs, I can see ...
Simulation
TingJiangT_Intel's avatar
TingJiangT_Intel
Icon for Contributor rankContributor
2 years ago

As it worked fine after you changed the project, the error may related to the project and testbench. It may be that your project got stuck during simulation, causing excessive CPU resource usage.

You may check your testbench to see if there are any operations that cause an infinite loop.


  • c-thaler's avatar
    c-thaler
    Icon for Occasional Contributor rankOccasional Contributor
    2 years ago

    Thanks for the reply.

    Questa is able to detect zero delay loops, so I should see an error about this. Furthermore, most of the time the tests run just fine. I have to run a single test a few hundred times to cause this behavior. That means it is nondeterministic behavior. If there is an infinite zero delay loop I should see the hang up in every simulation run.
    Besides that, I should be able to break/pause simulation in such a loop, which does not work either.

  • c-thaler's avatar
    c-thaler
    Icon for Occasional Contributor rankOccasional Contributor
    2 years ago

    I was able to reproduce with the other project, too. It took a few thousand simulation runs over the weekend. But finally it got stuck with 100% CPU load.