tests/python/unittest/test_engine.py

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import mxnet as mx
import os
from mxnet.test_utils import environment
import pytest

def test_bulk():
    with mx.engine.bulk(10):
        x = mx.nd.ones((10,))
        x *= 2
        x += 1
        x.wait_to_read()
        x += 1
        assert (x.asnumpy() == 4).all()
        for _ in range(100):
            x += 1
    assert (x.asnumpy() == 104).all()

@pytest.mark.skip(reason="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 environment('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))
            assert omp_max_threads == 1