Similar time taken under different timestep sizes

Yu Wang_21521
Yu Wang_21521 Altair Community Member
edited January 8 in Community Q&A

Dear Sir/Madam,

 

When I was applying EDEM for a long-term simulation under the timestep size of 9e-07 and 8e-07s, I found the time taken were quite similar, both are close to 30 days. I suppose the time taken would be quite different under such conditions, as the smaller timestep requires more calculation efforts. May I know the reason for this similarity issue?

 

Best Regards,

Yu

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Answers

  • Richard Wood_20774
    Richard Wood_20774
    Altair Employee
    edited January 8

    Hi,

    Could be a few reasons, but that's indicating that the majority of your computational expense lies elsewhere. Could be a factory, could be data write out, could be passing data from CPU to GPU, hard to say without knowing more.

    Using a smaller timestep clearly means more timesteps to execute, but if your machine takes 1e-6s to perform a timestep say (that is a complete made up number) but when you save data it's taking a day per data write out (.h5 save), then you aren't going to notice the small difference in the number of extra timesteps as the data save is what takes all the effort. As I say, without knowing more about your particular case it's hard to say, but my point is there are more factors at play than just the timestep size.

    Cheers,

    Richard

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