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April 23, 2024 at 1:30 pmMike H.Subscriber
Hello,
Sorry for the lack of specific information, but I just wanted to ask about the following issue:
Issue: Chemkin Uncertainty analysis using multiple cores hangs on the first round of runs (107 total runs). This is in 2024R1 using eight cores.Â
Computer: AMD Epyc Rome, two processor workstation, 24 cores total, 64 GB RAM, Windows 10 pro.
Troubleshooting: The exact same analysis runs fine in 2023R2 (same case file too).
Questions: were there any significant changes to Chemkin 2024R1 that would causes this behavior? Did the default MPI change? Also, can I change the MPI that Chemkin uses? I find that in Fluent I have to change the default MPI to get good parallel performance with AMD processors.
Thanks!
-Mike
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April 24, 2024 at 9:32 pmjcooperAnsys Employee
Hi Mike:
I would suggest trying a regular parallel run to rule out issues with MPI, and/or test a very simple case in parallel, such as a closed reactor.
ANSYS Forte 2024R1 uses MPI 2021 and MPI 2018, so I imagine Chemkin would be the same. To be safe, you can try installing the MPI that comes with the 2024 release:
Best Regards
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April 25, 2024 at 12:38 pmMike H.Subscriber
Judy,
Thank you for the response. Maybe I used the wrong terminology, but I am not trying to run across different machines; I have a stand-alone machine with two processors with 10 cores each. The uncertainty analysis, I believe, does a separate solver for each case on a different core. But, I will try a simple parallel solve case (not uncertainty analysis).
For reference, in Fluent on my AMD machine, the Intel MPI is slow. I had to change it to MSMPI to get the proper speed.
Thanks!
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April 25, 2024 at 3:34 pmjcooperAnsys Employee
I wasn't assuming anything about distributed parallel etc ... Only think its a good idea to eliminate complexity when running tests on parallel execution.
This type of thing is probably a bit beyond Forum support, since it is probably a systems issue. If problems persist with simple cases, I would advise following up with your local IT.
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April 25, 2024 at 6:18 pmMike H.Subscriber
Thank you again Judy. Quick question: how do I run a single chemkin case in parallel in the GUI?Â
I only see this option under preferences: "Number of Parameter Study Runs to Run in Parallel."
Are any of the Chemkin Sample files set up to run a reactor across multiple cores?
Thanks! -Mike
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April 25, 2024 at 6:54 pmjcooperAnsys Employee
Hi Mike:
Chemkin is a serial process unless you are doing a parametric analysis. For parametric runs, the number of parametric points that are done in parallel can be controlled thorugh the preferences:
If you set the number to 1, your parametric points will be run in serial instead of simultaneously.
Best Regards,
Judy
Â
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April 26, 2024 at 1:00 pmMike H.Subscriber
Judy,
Thanks again for the response. Now I am having trouble running a single case in 2024R1 vs 2023R2. Both have the same error tolerances. The 2024R1 just hangs and gets stuck at 100% in the solver window.
However, I did not have issues running a sample PFR case in 2024R1. So, it must be specific to my case. I can't really share my input files due to privacy concerns, but it is a 21 reaction and 16 species PFR with the SRK equation of state.
For now, I will default back to 2023R2. Maybe in the future, I can spend more time troubleshooting.
Best regards.
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