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Fluids

fluent 2022 r1 slow bandwitdth

    • kevin1986
      Subscriber

      Hi guys,

      I installed ansys 2022 r1, 2019 r1 and 2022 r1. I use these different ansys fluent to run my test case. I found fluent 2022 r1 is much slower than others. I am quite confused since the hardware (cpu and memory) is the same. After further debugging, I found fluent 2022 r1's bandwidth (slowest is around 100 mb/s, fasters is 2000 mb/s, but the value changes every time) is much slower than others (slowest is around 1500 mb/s).  All of them I used intelmpi, with 64 cores. 

      What can I do?

      Thanks. 

    • kevin1986
      Subscriber

       

      I also tried 2022r2. Still slow. I tried only 4 cores. 2020’s bandwidth is around 9000-10000, 2022r2 is around 1000-2000. When more cores are used, 2022r2 is slower. Why?

       

      • Mangesh Bhide
        Ansys Employee

        Hello,

        we could compare two different Fluent versions on same machine or same Fluent version on twi different machines, but not 2 different versions on 2 different computers at the same time..

        Are the screenshots from two differrent machines or two different user profiles on same machine? Is there variation seen on the same machine with 2 different versions of Fluent and MPI or are we comparing this data from 2 different machines ?

        If only one machine is used for solcing then please also try microsoft MPI from lauuncher parallel settings

        If still seeing issues then can you please provide processor make and model, memory quantity and configuration (4 DIMMs of 8 GB etc)

    • kevin1986
      Subscriber

      I think its because the new version uses intelmpi2019, but the old version uses intelmpi 2018.  

      Is it possible to let ansys fluent 2022 to use intelmpi 2018?

    • kevin1986
      Subscriber

      In the parallel switch, after typing "intel2018" I can use intelmpi2018. I did several tests, intelmpi2018 is better than intelmpi2019 (intel). But its still slow. I cannot figure out why.

    • kevin1986
      Subscriber

      The slow parallel bandwidth makes the calculation in Fluent 2022 much slower than that of Fluent 2020...

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