Stats

  • Locked Locked
  • Replies 1
  • Subscribers 124
  • Views 2063
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

APS

FormerMember
FormerMember

Hello,

I've enjoying APS mode when I simulate a big schematic.

Of course, I leave it blank for process affinity and set it auto for multithread option.

But, I realized that when simulation runs on APS mode, total CPU usage is depending on the size of schematic and availability of CPU.

I mean, even if no one use CPU so that I could use 1600% CPU, only 200% or 300% CPU is used if my schematic is not big enough. 

As you know, the simulation time is generally depending on not only the schematic size but also "CLK speed". For example, if we run a simulation with a simple inverter, it may take long time if CLK speed is , for instance, 10GHz. 

So, what I want to ask you here is:

is there any certain way to use FULL CPU regardless of the size of the schematic?

Generally, I am the only user of our server so I can use FULL CPU(2400%).

I heard from my colleague that there is a certain way to use FULL CPU even with a small schematic. 

Thank you so much!

  • First of all, the "auto" number of threads in APS is a maximum of 8. It would not pick 24 if 24 are available. However, see the point below - increasing this beyond a certain level won't help.

    Secondly, Amdahl's Law has an effect here. You cannot keep adding more CPUs and seeing improvement. In particular, for smaller circuits, the speed up in solving multiple smaller matrices would be outweighed by the work needed to combine the results together - similarly the cost of managing the threads doing the model equation evaluation.

    Note that the simulation speed isn't down to the clock speed - although the number of time steps in the simulation has a big influence. 

    Since MMSIM13.1.1 version of spectre, you can run with +diagnose on the command line and this can give some pointers as to what is impacting the speed of your simulation - so you might want to try that.

    Kind Regards,

    Andrew.

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.