Does OpenMP work without releasing the GIL?

Should the Py_BEGIN_ALLOW_THREADS / Py_END_ALLOW_THREADS be put here or at the Python extension? I guess at the Python extension, since the lib is Python-independent.

My understanding was that the GIL doesn't come into play here because there
aren't any python threads or references to python objects, and thus no
python bytecode running through the interpreter; some preliminary
performance profiling seems to indicate that's the case. I could be wrong
though.

On Fri, Oct 24, 2014 at 10:44 AM, Luiz Irber notifications@github.com
wrote:

In lib/hashtable.cc:

     n_consumed++;
 }

• for (unsigned int i=0; i<s.length()-_ksize; ++i) {

• }
• */
• std::vector hashes;
• while(!kmers.done()) {

•    hashes.push_back(kmers.next());
  

• }
• #pragma omp parallel

Does OpenMP work without releasing the GIL?

Should the Py_BEGIN_ALLOW_THREADS / Py_END_ALLOW_THREADS be put here or at
the Python extension? I guess at the Python extension, since the lib is
Python-independent.

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Camille Scott

Department of Computer Science and Engineering
Lab for Genomics, Evolution, and Development
Michigan State University

camille.scott.w@gmail.com

On Fri, Oct 24, 2014 at 07:48:30AM -0700, Camille Scott wrote:

     n_consumed++;
 }

• for (unsigned int i=0; i<s.length()-_ksize; ++i) {
• }
• */
• std::vector hashes;
• while(!kmers.done()) {

•    hashes.push_back(kmers.next());
  

• }
• #pragma omp parallel

My understanding was that the GIL doesn't come into play here because there
aren't any python threads or references to python objects, and thus no
python bytecode running through the interpreter; some preliminary
performance profiling seems to indicate that's the case. I could be wrong
though.

As you say.

Plus, it'd crash. CPython is pretty good about crashing in this kind of
situation.

Note: move these inside try {} block.

This link says only the OpenMP master thread can deal with exceptions, so there might be another changes lurking here.

Note to self / general: We care very much, because unsigned ints have module sizeof behavior (they loop back around to zero).