fix flaky test: test_broadcast_binary_op (apache#11875)

* cast inputs to f32

* retrigger

* retrigger

* remove extra cast

* remove commented out function

* retrigger

tests/python/unittest/test_operator.py

@@ -1844,7 +1844,6 @@ def test_bmod(a, b):
         #c = a % b
         c = mx.sym.cast(a, dtype='float64') % mx.sym.cast(b, dtype='float64')
         # '%' is sensitive to the precision of the calculation.  Force numpy to match mxnet's float32.
-        #check_binary_op_forward(c, lambda a, b: np.float32(a) % np.float32(b), gen_binary_data)
         check_binary_op_forward(c, lambda a, b: np.float32(a) % np.float32(b), gen_binary_data, rtol=0, atol=0)
         check_binary_op_backward(c,
             lambda g_out, a, b: (g_out, - g_out * (np.float32(a) // np.float32(b))), gen_binary_data)
@@ -1913,10 +1912,16 @@ def test_bdiv(a, b):
         check_binary_op_forward(c, lambda a, b: a / b, gen_broadcast_data, mx_nd_func=mx.nd.divide)
         check_binary_op_backward(c, lambda g_out, a, b: (g_out / b, - g_out * a / (b * b)), gen_broadcast_data)
 
-    def test_bmod(a, b):
+    def test_bmod(a_, b_):
+        # Python and numpy operate only in double so to avoid numerical errors we have to use
+        # doubles as well. This was a flaky test before when using float32. seed 1688524483, 1768433044
+        a = mx.sym.cast(a_, dtype='float64')
+        b = mx.sym.cast(b_, dtype='float64')
+        # '%' is sensitive to the precision of the calculation.  Force numpy to match mxnet's float32.
         c = mx.sym.broadcast_mod(a, b)
         check_binary_op_forward(c, lambda a, b: a % b, gen_broadcast_data, atol=1, mx_nd_func=mx.nd.modulo)
-        check_binary_op_backward(c, lambda g_out, a, b: (g_out, - g_out * (a // b)), gen_broadcast_data, atol=1)
+        check_binary_op_backward(c,
+                                 lambda g_out, a, b: (g_out, - g_out * (np.float32(a) // np.float32(b))), gen_binary_data)
 
     def test_bmod_int(a, b):
         c = mx.sym.broadcast_mod(mx.sym.cast(a, dtype='int32'), mx.sym.cast(b, dtype='int32'))
@@ -1974,13 +1979,7 @@ def test_bxor(a, b):
     test_bminus(a, b)
     test_bmul(a, b)
     test_bdiv(a, b)
-    '''
-    Flaky Test Disabled due to master build failure:
-    http://jenkins.mxnet-ci.amazon-ml.com/blue/organizations/jenkins/incubator-mxnet/detail/master/1248/pipeline
-    Github Issue: https://github.com/apache/incubator-mxnet/issues/11838
-
     test_bmod(a, b)
-    '''
     test_bmod_int(a, b)
     test_bpow(a, b)
     test_bequal(a, b)