# OpenMC 0.14.0 Shared-Memory Parallelism not working

**URL:** <https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696>\
**Category:** User Support\
**Created:** [November 30, 2023, 1:48am UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696 "2023-11-30T01:48:28Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Donald](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Donald](https://openmc.discourse.group/u/Donald)\
**Post date:** [November 30, 2023, 1:48am UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696/1 "2023-11-30T01:48:28Z")

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I have installed OpenMC 0.14.0 from the source on macOS Catalina, it has installed successfully and will run but settings the OMP\_NUM\_THREADS environment variable to the number of hardware threads on the computer still results in OpenMC running a single process?

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**Author:** ![pshriwise](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pshriwise/32/3863_2.png) [@pshriwise](https://openmc.discourse.group/u/pshriwise)\
**Post date:** [November 30, 2023, 6:20pm UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696/2 "2023-11-30T18:20:15Z")

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Hi @Donald,

Thanks for your post! Does your machine have an Apple silicon chip (M1 or M2 chip). If so, the native compilers provided through XCode don’t provide support for OpenMP threading.

Not worry though, other versions of clang can be installed on the latest Apple machines and support threading. I’ll try to track down a link to them if needed.

Best,

Patrick

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**Author:** ![Donald](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Donald](https://openmc.discourse.group/u/Donald)\
**Post date:** [November 30, 2023, 7:22pm UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696/3 "2023-11-30T19:22:20Z")

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Hi @pshriwise,

Thank you fo r your reply. My machine does not have an Apple silicon chip.

gcc version if helpful is:  
Apple clang version 12.0.0 (clang-1200.0.32.29)

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<div class="post-metadata">

**Author:** ![pshriwise](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/pshriwise/32/3863_2.png) [@pshriwise](https://openmc.discourse.group/u/pshriwise)\
**Post date:** [November 30, 2023, 7:48pm UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696/4 "2023-11-30T19:48:37Z")

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> [@Donald](#):
>
> Apple clang version 12.0.0 (clang-1200.0.32.29)

Ah, I see. I’m betting that the OpenMP library still isn’t supported by default. Perhaps this link is helpful?

[https://open-box.readthedocs.io/en/latest/installation/openmp\_macos.html](https://open-box.readthedocs.io/en/latest/installation/openmp_macos.html)

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<div class="post-metadata">

**Author:** ![Donald](https://avatars.discourse-cdn.com/v4/letter/d/ac8455/32.png) [@Donald](https://openmc.discourse.group/u/Donald)\
**Post date:** [December 1, 2023, 1:20am UTC](https://openmc.discourse.group/t/openmc-0-14-0-shared-memory-parallelism-not-working/3696/5 "2023-12-01T01:20:06Z")

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Looks like the issue is OpenMP not being supported, went though the instructions you included and got the following error when running make:  
clang: **warning:** argument unused during compilation: ‘-Xclang -fopenmp’ [-Wunused-command-line-argument]  
So looks like it is a clang with OpenMP issue, haven’t found a work around