larroy 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_r355861938
##########
File path: tests/python/unittest/test_engine.py
##########
@@ -30,6 +33,44 @@ def test_bulk():
x += 1
assert (x.asnumpy() == 104).all()
[email protected]("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))
+ try:
+ wfd.close()
+ except:
+ pass
+ try:
+ (cpid, status) = os.waitpid(pid, 0)
+ assert cpid == pid
+ exit_status = status >> 8
+ assert exit_status == 0
+ except:
+ pass
+ else:
+ os.close(w)
+ rfd = os.fdopen(r, 'r')
+ rfd.read(1)
+ omp_max_threads = mx.base._LIB.omp_get_max_threads()
+ print("Child omp max threads: {}".format(omp_max_threads))
Review comment:
let's leave it for now, as nosetest adsorbs stdout output anyway. So
basically unit test is the only place where prints are acceptable.
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