Low performance on AMD Epyc in Fluent

- May 18, 2023 at 5:46 am
  
  Otari Kemularia
  Subscriber
  
  I tested the same Fluent setup on 3 different machines. Both AMD cpus 5800x and 2x Epyc 7532 are experiencing declining performance as the used core number increases. While, 2xE5-2697A has rising performance up to 8 cores (since the Fluent setup itself isn't very heavy).
  I looked up for the similar problems and the most common reason appears to be somehow conntected to msmpi.
  Could it be somehow connected to CPU or Chipset drivers? I'm using Win 10 Pro N, should I be using Windows server?
  
  As for the BIOS settings, I'm using whatever AMD is recommending for the Fluent.
- May 19, 2023 at 7:30 pm
  
  Rahul Kumar
  Ansys Employee
  
  Hello,
  You mention that you test Fluent SETUP, did you test using the same model (same mesh size, physics and setup)? The total time in the graph - Is it wall clock time or the simulation time?
  In some cases, using more number of cores actually reduces the performance. See this section of the user's guide: 40.9. Checking and Improving Parallel Performance (ansys.com). I would also suggest to not display any report definitions (any graphics) while running the simulation if you are testing the wall clock time.