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How to use FLUENT only in single processing mode

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Old   January 15, 2018, 01:16
Unhappy How to use FLUENT only in single processing mode
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Bernd
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Hello,
I am really new to ANSYS and Fluent. I have created my environment in which I want to simulate. When I try to set up my UDF I always get the following error:
"Error: The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform (win64)"
and:
"Error Object: #f"

When I scrolled through the control panel I saw the warning:
************************************************** ********
* WARNING: Automatically switched to run in parallel -t1 mode. *
* Detected non-parallelized UDF usage, enabling parallel usage. *
* If you encounter any issues, please re-run with -t0 flag. *
************************************************** ********

Even if I start Fluent with the -t0 flag as mentioned it will always swap to parallel processing.

How else can I suppress that Fluent swaps in parallel processing mode? Because my UDF only works in single processing.

Thank you in advance
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Old   January 15, 2018, 16:19
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Passing the -t flag with any number will launch Fluent in parallel mode. Just don't pass any -t or -p or -pe flag. e.g. just launch using fluent 3ddp
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Old   April 23, 2018, 10:05
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Hi Bernd_Huegges,
I am facing the same problem. My UDF is working good for ANSYS 18.0 but when the same UDF is using in ANSYS 19.0, then Fluent is showing the error exactly like your case. Have you overcome with your problem? Help me if you have resolved this problem, I would be thankful to you.
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Old   April 23, 2018, 12:26
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Since v18.2 Fluent no longer has a serial mode, only a parallel mode with a single process (equivalent to -t1). If you want the original serial mode then you need to use the -t0 flag.

With that said, the warning is because the UDF is not parallelized. Either parallelize your UDF or run Fluent in serial mode if your version is less than 18.2 or pass -t0 as an launch flag in 18.2 and onwards.

Last edited by LuckyTran; April 23, 2018 at 20:34.
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Old   April 24, 2018, 03:48
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Hi LuckyTran,
Thanks for your reply. But my problem could not be resolved as I am new to the ANSYS. Can you please explain, how I play with t-o, t-1 flag.
You can also mail me at khandelwaldeepak93@gmail.com.
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Old   May 2, 2018, 08:05
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no solution for this ?
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Old   May 15, 2018, 18:07
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solution please :/
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Old   September 14, 2021, 15:33
Default what is launch flag in fluent?
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Easier way is to just select parallel option and select "0" in the processes option.
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Old   September 17, 2021, 02:43
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for windows:
open command prompt and execute:
4 cores (parallel) with double precision solver
Code:
fluent 3ddp -t4
single core (not parallel)
Code:
fluent 3ddp -t0
1 node 1 host (parallel)
Code:
fluent 3ddp -t1
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Old   August 3, 2022, 06:37
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Juan
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Thanks, AlexanderZ, for the solution. I can launch fluent with -t1 flag. However, launching with the -t0 flag does not work with Fluent 2021 R1. The following error message popped up:

"The code execution cannot proceed because hdf5.dll was not found. Reinstalling the program may fix this problem."

My reason to use serial mode is to use a UDF that eventually I'll have to modify to use in parallel mode so if you can share an example with DEFINE_ADJUST and
DEFINE_PROPERTY macros, it would be appreciated. I found some examples in this forum but I couldn't make it work yet.
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Old   August 4, 2022, 01:43
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open new thread on forum, explain your request, share your UDF

you may find information regarding parallelizaing code by looking for Parallel Considerations in Ansys Fluent Customization manual
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