Learning Forum

[Mike H.]

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. 

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

[jcooper]

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

[Mike H.]

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!

[jcooper]

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.

[Mike H.]

Thank you again Judy. Quick question: how do I run a single chemkin case in parallel in the GUI? 

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

[jcooper]

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

 

[Mike H.]

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.