Using multi cores/processors in System Coupling

- September 9, 2019 at 3:23 pm
  
  kfouladi
  Subscriber
  
  Hi,
  
  I like to know if there is an option to use multiple cores/processor when running FSI system coupling. I specified 5 cores in Mechanical and parallel processing with 8 cpu for Fluent. However, the run crashes when it reach Fluent. Any suggestions?
  
  Kamran
- September 10, 2019 at 9:59 am
  
  Rob
  Ansys Employee
  
  Does Fluent crash or fail to launch? What happens if you try in serial and with the same number of cores in parallel?
- September 10, 2019 at 6:05 pm
  
  kfouladi
  Subscriber
  
  It works fine if "Serial" processing option is selected for Fluent, even if I chose 4 cores under "My computer" in Mechanical (Distributed selected). However, it does crash when I change to "Parallel" in Fluent. I tried to use the same number of cores for both: 4 cores in Mechanical (under "My Computer, with Distributed selected) and 8 processors (I believe it is 4 cores) for Fluent. These are messages I get:
  
  "Update failed for the Solution component in System Coupling. The SC Service crashed or ended unexpectedly." I also get "DP(0) A solver failure occurred during the run in Fluid Flow (Fluent) system.
  
  -Kamran
- September 11, 2019 at 9:03 am
  
  Rob
  Ansys Employee
  
  Can you save the Fluent case & data from a serial run & then try it outside of the workflow in parallel? I'm wondering if it's something in Fluent rather than the coupling. Do you have any UDFs active, and what other models are on in Fluent?
- September 11, 2019 at 6:40 pm
  
  kfouladi
  Subscriber
  
  Yes, I had an active UDF (EXECUTE_AT_END). I removed the UDF and it works now. Thanks.
  
  Is multi-core/processing incompatible with UDF?
- January 22, 2021 at 9:58 am
  
  Ahmed_Aissa
  Subscriber
  
  It is a common problem that people fail to run parallel simulations when a UDF is implemented within Fluent. If you try to debug the error from the Fluent side, you will notice an error of type makedir which prevent the UDF to be executed in parallel. To overcome this issue, you need to implement a recent version of Visual Studio and from the working directory of your Fluent job, open a command line (Cross tools command prompt) and open Fluent launcher from \User\Programe file\Ansys Inc\'your versiontbin\win64 (If you are using Windows). I am not sure if you can use the same method to open Workbench (From the Workbench working directory) but it is worth trying. n
- January 22, 2021 at 10:35 am
  
  Rob
  Ansys Employee
  
  close, but in the recent builds, 2020R1 and on we can also use the CLANG compiler that installs along with Fluent. n

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