Set dtype of compare op's output to bool (#21864)

* add unittests, test=develop

* set dtype of compare op to bool, test=develop

python/paddle/fluid/layers/math_op_patch.py

@@ -27,6 +27,8 @@ _supported_int_dtype_ = [
     core.VarDesc.VarType.INT64,
 ]
 
+compare_ops = ['__eq__', '__ne__', '__lt__', '__le__', '__gt__', '__ge__']
+
 
 def monkey_patch_variable():
     def unique_tmp_name():
@@ -224,7 +226,12 @@ def monkey_patch_variable():
                 self = other_var
                 other_var = tmp
 
-            out = create_new_tmp_var(current_block(self), dtype=lhs_dtype)
+            # NOTE(zhiqiu): the output of compare operator should be bool.
+            if method_name in compare_ops:
+                out = create_new_tmp_var(current_block(self), dtype="bool")
+            else:
+                out = create_new_tmp_var(current_block(self), dtype=lhs_dtype)
+
             axis = -1
             if other_var.shape[0] == -1:
                 axis = 0

python/paddle/fluid/tests/unittests/test_math_op_patch.py

@@ -200,6 +200,46 @@ class TestMathOpPatches(unittest.TestCase):
         b_np_actual = (a_np / 7).astype('int64')
         self.assertTrue(numpy.array_equal(b_np, b_np_actual))
 
+    @prog_scope()
+    def test_equal(self):
+        a = fluid.layers.data(name="a", shape=[1], dtype='float32')
+        b = fluid.layers.data(name="b", shape=[1], dtype='float32')
+        c = (a == b)
+
+        place = fluid.CPUPlace()
+        exe = fluid.Executor(place)
+        a_np = numpy.array([3, 4, 10, 14, 9, 18]).astype('float32')
+        b_np = numpy.array([3, 4, 11, 15, 8, 18]).astype('float32')
+
+        c_np, = exe.run(fluid.default_main_program(),
+                        feed={"a": a_np,
+                              "b": b_np},
+                        fetch_list=[c])
+
+        self.assertTrue(numpy.array_equal(c_np, a_np == b_np))
+        self.assertEqual(c.dtype, fluid.core.VarDesc.VarType.BOOL)
+
+    @prog_scope()
+    def test_equal_and_cond(self):
+        a = fluid.layers.data(name="a", shape=[1], dtype='float32')
+        b = fluid.layers.data(name="b", shape=[1], dtype='float32')
+
+        one = fluid.layers.ones(shape=[1], dtype='int32')
+        zero = fluid.layers.zeros(shape=[1], dtype='int32')
+        cond = (one == zero)
+        c = fluid.layers.cond(cond, lambda: a + b, lambda: a - b)
+
+        place = fluid.CPUPlace()
+        exe = fluid.Executor(place)
+        a_np = numpy.array([3, 4, 10, 14, 9, 18]).astype('float')
+        b_np = numpy.array([3, 4, 11, 15, 8, 18]).astype('float')
+        c_np, = exe.run(fluid.default_main_program(),
+                        feed={"a": a_np,
+                              "b": b_np},
+                        fetch_list=[c])
+
+        self.assertTrue(numpy.array_equal(c_np, a_np - b_np))
+
     @prog_scope()
     def test_neg(self):
         a = fluid.layers.data(name="a", shape=[10, 1])