OPTISTRUCT : why the results are different if using different number of CPU cores？

User: "Yinghao_Mei_2025"
Yinghao_Mei_2025
Altair Community Member

Hello, I am doing the frequency response analysis of a chassis structure. I found the result will be different I choose different number of CPU cores. I calculate the same FEM file by adding -nt 2 or -nt 8. The pictrue is the result of displacement response result. I can't attach the FEM file, but I am sure I was using the same FEM file. Is it normal to have different result? thank you.

difference.png

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    User: "Kranzeder"
    Kranzeder
    Altair Employee

    Hi
    Difficult to give a precise answer here.
    Although I find the difference not significant in terms of FE accuracy
    I have 2 theories.


    1:
    In case you are dealing with very small response values there could be the chance differences
    occur because of numerical rounding.
    Looks to me like the curves are matching for higher values.

    2:
    The model itself could have an issue and for that could be numerical unstable.
    Changing machines, version or -nt …. may trigger such effects

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