utilize more than one logical cpu

  • Last Post 25 October 2017
  • Topic Is Solved
bombaglad posted this 25 October 2017


when doing any kind of simulations with ansys AIM 18.2, the solver seems to never use over 30% of the CPU capacity on my i3-5005U, and over 750MB of my 8GB RAM. now, i know that this is by no means a high end setup, but i still don't get why the program essentially uses only one logical CPU. when doing a FEM analysis in catia, it uses all the cpu it can get, but this program seems to limit itself without any reason. i haven't found any setting that would help, nor any other way to force the program to simulate faster. any ideas?

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peteroznewman posted this 25 October 2017

First click on the Physics block, then under Physics Solution click the Solver Options link, then select Launch Controls 1.


I have a 4-core laptop that is configured for hyperthreading which allows two threads per core, so the Task Manager Performance tab shows 8 CPUs. You should only type in 4 not 8 for the number of processors in this example. ANSYS will only reach about 50% utilization on the Task Manager Performance tab as it uses "real" cores, not threads.

The default is 2 processors, so if you have a 4-core computer with hyperthreading turned on, you would expect to see an average of 25% usage on the Task Manager while the solver is running on 2 cores.

I also have a 16-core desktop where I disabled hyperthreading (per ANSYS recommendations) and I can see 100% utilization on the Task Manager when ANSYS is running and I let it use all 16 cores.


When I am using ANSYS Mechanical rather than AIM, I can see if the solver is running in RAM only (incore) or needs to use the disk (out-of-core) because the solver estimated that it could not run in RAM only. When I see the solver is running out-of-core, I might choose to stop the solution and reduce the mesh density to try to get an incore solution, which will take less time to solve. I don't think AIM has that degree of visibility on how it is solving, but since it uses the same solver, I assume it tries to solve in RAM if possible.



bombaglad posted this 25 October 2017

wow, thanks a lot, this totally does the job