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Simulation time increase?

Sparsh Gupta

I have added some coverpoints to my testbench, which hare getting sampled at every posedge. This has increased my simulation time 10x time. Is this a fairly likely occurrence? Or, there is a way to optimize this.

Parents

  • It's certainly not impossible that you could make the simulation run much slower like this, but without any information about how your coverpoints are defined, how complex (or not) the rest of your code is, it's impossible to know if 10x is reasonable or not. Generally it's a bad idea to sample coverpoints on every clock; typically you should only sample when there is something valid to sample. E.g. for an address bus, you would only want to sample on the cycles where the address is actually used by the DUT.

    Having lots of complex bin declarations might slow the simulator down, but again there isn't any generic formula to say how much performance impact your code would have!

    Since you most likely don't want to share all your code here, why not get your local Cadence AE to visit and review your code with you? The AE team has lots of experience writing and reviewing coverage code so they should be able to give you some guidance.

Reply

  • It's certainly not impossible that you could make the simulation run much slower like this, but without any information about how your coverpoints are defined, how complex (or not) the rest of your code is, it's impossible to know if 10x is reasonable or not. Generally it's a bad idea to sample coverpoints on every clock; typically you should only sample when there is something valid to sample. E.g. for an address bus, you would only want to sample on the cycles where the address is actually used by the DUT.

    Having lots of complex bin declarations might slow the simulator down, but again there isn't any generic formula to say how much performance impact your code would have!

    Since you most likely don't want to share all your code here, why not get your local Cadence AE to visit and review your code with you? The AE team has lots of experience writing and reviewing coverage code so they should be able to give you some guidance.

Children
  • in reply to StephenH

    In my experience with huge coverage models, containing many bins, I didn't necessarily notice a decrease in simulation performance, but a huge increase in the duration of the final coverage dump step (after simulation has ended). Sampling too often is a more likely culprit.

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