[GitHub] [incubator-mxnet] cjolivier01 edited a comment on issue #14979: [BUG] Using a package with MKL and GPU versions, using python to open a new process will cause an error

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cjolivier01 edited a comment on issue #14979: [BUG] Using a package with MKL and GPU versions, using python to open a new process will cause an error
URL: https://github.com/apache/incubator-mxnet/issues/14979#issuecomment-563250878
 
 
   If it’s gone with the upgrade, then fine.  
   
   
   However, if it’s not, and since it also happened with official dist of libiomp5, then considering that llvm omp is in HUGE distribution globally being part of clang and all, then it seems pretty unlikely to me that it’s a bug in the openmp causing this. Especially since I wrote most of this omp-related stuff in mxnet that is in that stack trace, and I definitely didn’t test it specifically with forking — it wasn’t a use case at the time. in fact, at the time i wrote that, it was known that trying to use omp at all (with libgomp specifically) would hang if attempted in a forked process (there’s a PR in there somewhere fixing the issue by avoiding using a kernel i seem to recall — it was a long time ago and before llvm openmp was added). generally this wasn’t a problem because the OMP_NUM_THREADS gets set to 1 in the atfork call by the engine code.
   
   However, if mxnet is loaded *after* the fork, then that environment variable was never set because the engine code never ran to hook the fork call before then. I think it’s possible there’s a bug in the (my) mxnet omp code since this wasn’t a use-case considered.  This would mean it would likely still occur with clang builds (assuming it’s not intermittent and hard to reproduce).

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