[GitHub] [incubator-mxnet] apeforest commented on a change in pull request #16999: Prevent after-fork number of OMP threads being bigger than 1.

[GitBox <gi...@apache.org>]

apeforest commented on a change in pull request #16999: Prevent after-fork number of OMP threads being bigger than 1.
URL: https://github.com/apache/incubator-mxnet/pull/16999#discussion_r355102472
 
 

 ##########
 File path: tests/python/unittest/test_engine.py
 ##########
 @@ -30,6 +33,44 @@ def test_bulk():
             x += 1
     assert (x.asnumpy() == 104).all()
 
+@unittest.skip("OMP platform dependent")
+def test_engine_openmp_after_fork():
+    """
+    Test that the number of max threads in the child is 1. After forking we should not use a bigger
+    OMP thread pool.
+
+    With GOMP the child always has the same number when calling omp_get_max_threads, with LLVM OMP
+    the child respects the number of max threads set in the parent.
+    """
+    with EnvManager('OMP_NUM_THREADS', '42'):
+        r, w = os.pipe()
+        pid = os.fork()
+        if pid:
+            os.close(r)
+            wfd = os.fdopen(w, 'w')
+            wfd.write('a')
+            omp_max_threads = mx.base._LIB.omp_get_max_threads()
+            print("Parent omp max threads: {}".format(omp_max_threads))
 
 Review comment:
   Please remove print statement from test.

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