add unary operator __neg__, test=develop (#21787)

adds unary operator __neg__ for VarBase in dygraph mode, and for Variable in static graph mode.

python/paddle/fluid/dygraph/math_op_patch.py

@@ -35,11 +35,7 @@ def monkey_patch_math_varbase():
     """
 
     def safe_get_dtype(var):
-        try:
-            dtype = var.dtype
-        except:
-            raise ValueError("Cannot get data type from %s", var.name)
-        return dtype
+        return var.dtype
 
     @no_grad
     def create_tensor(value, dtype, shape):
@@ -117,6 +113,9 @@ def monkey_patch_math_varbase():
         outs = core.ops.scale(inputs, attrs)
         return outs['Out'][0]
 
+    def _neg_(var):
+        return _scalar_elementwise_op_(var, -1.0, 0.0)
+
     def _scalar_elementwise_add_(var, value):
         return _scalar_elementwise_op_(var, 1.0, value)
 
@@ -217,6 +216,7 @@ def monkey_patch_math_varbase():
 
         setattr(core.VarBase, method_name,
                 _elemwise_method_creator_(method_name, op_type, reverse,
-                                          scalar_method))
-
+                                          scalar_method)),
+    # b = -a
+    core.VarBase.__neg__ = _neg_
     core.VarBase.astype = astype

python/paddle/fluid/layers/math_op_patch.py

@@ -157,6 +157,9 @@ def monkey_patch_variable():
                    "bias": bias})
         return out
 
+    def _neg_(var):
+        return _scalar_elementwise_op_(var, -1.0, 0.0)
+
     def _scalar_elementwise_add_(var, value):
         return _scalar_elementwise_op_(var, 1.0, value)
 
@@ -273,5 +276,6 @@ def monkey_patch_variable():
         setattr(Variable, method_name,
                 _elemwise_method_creator_(method_name, op_type, reverse,
                                           scalar_method))
-
+    # b = -a
+    Variable.__neg__ = _neg_
     Variable.astype = astype

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

@@ -200,6 +200,19 @@ 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_neg(self):
+        a = fluid.layers.data(name="a", shape=[10, 1])
+        b = -a
+        place = fluid.CPUPlace()
+        exe = fluid.Executor(place)
+        a_np = numpy.random.uniform(-1, 1, size=[10, 1]).astype('float32')
+
+        b_np = exe.run(fluid.default_main_program(),
+                       feed={"a": a_np},
+                       fetch_list=[b])
+        self.assertTrue(numpy.allclose(-a_np, b_np))
+
 
 if __name__ == '__main__':
     unittest.main()

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

@@ -201,6 +201,13 @@ class TestMathOpPatchesVarBase(unittest.TestCase):
             res = (a >= b)
             self.assertTrue(np.array_equal(res.numpy(), a_np >= b_np))
 
+    def test_neg(self):
+        a_np = np.random.uniform(-1, 1, self.shape).astype(self.dtype)
+        with fluid.dygraph.guard():
+            a = fluid.dygraph.to_variable(a_np)
+            res = -a
+            self.assertTrue(np.array_equal(res.numpy(), -a_np))
+
 
 if __name__ == '__main__':
     unittest.main()