def test_openblas_threading(self):
          # gh-27036
          # Test whether matrix multiplication involving a large matrix always
          # gives the same (correct) answer
          x = np.arange(500000, dtype=np.float64)
          src = np.vstack((x, -10*x)).T
          matrix = np.array([[0, 1], [1, 0]])
          expected = np.vstack((-10*x, x)).T  # src @ matrix
          for i in range(200):
              result = src @ matrix
              mismatches = (~np.isclose(result, expected)).sum()
              if mismatches != 0:
  >               assert False, ("unexpected result from matmul, "
                      "probably due to OpenBLAS threading issues")
  E               AssertionError: unexpected result from matmul, probably due to OpenBLAS threading issues
  E               assert False