Fix check grad with multioutput (#4067)

Fix check grad with multi outputs

python/paddle/v2/framework/tests/op_test.py

@@ -85,7 +85,7 @@ def get_numeric_gradient(scope,
                          op,
                          inputs,
                          input_to_check,
-                         output_name,
+                         output_names,
                          delta=0.005,
                          in_place=False):
 
@@ -100,8 +100,11 @@ def get_numeric_gradient(scope,
     ctx = core.DeviceContext.create(core.CPUPlace())
 
     def get_output():
-        op.run(scope, ctx)
-        return np.array(scope.find_var(output_name).get_tensor()).sum()
+        sum = 0.0
+        for output_name in output_names:
+            op.run(scope, ctx)
+            sum += np.array(scope.find_var(output_name).get_tensor()).sum()
+        return sum
 
     tensor_to_check = scope.find_var(input_to_check).get_tensor()
     tensor_size = product(tensor_to_check.get_dims())
@@ -225,7 +228,7 @@ class OpTest(unittest.TestCase):
 
     def check_grad(self,
                    inputs_to_check,
-                   output_name,
+                   output_names,
                    no_grad_set=None,
                    in_place=False,
                    max_relative_error=0.005):
@@ -237,13 +240,16 @@ class OpTest(unittest.TestCase):
         if no_grad_set is None:
             no_grad_set = set()
 
+        if not type(output_names) is list:
+            output_names = [output_names]
+
         numeric_grads = [
             get_numeric_gradient(
                 self.scope,
                 self.op,
                 self.inputs,
                 input_to_check,
-                output_name,
+                output_names,
                 in_place=in_place) for input_to_check in inputs_to_check
         ]
         grad_names = [

python/paddle/v2/framework/tests/test_gradient_checker.py

@@ -12,7 +12,8 @@ class GetNumericGradientTest(unittest.TestCase):
         z = x + y
         scope = core.Scope()
         add_op = create_op(scope, "add", {'X': x, 'Y': y}, {'Out': z}, dict())
-        arr = get_numeric_gradient(scope, add_op, {'X': x, 'Y': y}, 'X', 'Out')
+        arr = get_numeric_gradient(scope, add_op, {'X': x,
+                                                   'Y': y}, 'X', ['Out'])
         self.assertAlmostEqual(arr.mean(), 1.0, delta=1e-4)
 
     def test_softmax_op(self):