Fix and omptimize flip API (#34379)

Author: sljlp

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

@@ -33,6 +33,8 @@ def test_static_graph(self):
             axis = [0]
             input = fluid.data(name='input', dtype='float32', shape=[2, 3])
             output = paddle.flip(input, axis)
+            output = paddle.flip(output, -1)
+            output = output.flip(0)
             place = fluid.CPUPlace()
             if fluid.core.is_compiled_with_cuda():
                 place = fluid.CUDAPlace(0)
@@ -43,7 +45,7 @@ def test_static_graph(self):
                           feed={'input': img},
                           fetch_list=[output])
             out_np = np.array(res[0])
-            out_ref = np.array([[4, 5, 6], [1, 2, 3]]).astype(np.float32)
+            out_ref = np.array([[3, 2, 1], [6, 5, 4]]).astype(np.float32)
             self.assertTrue(
                 (out_np == out_ref).all(),
                 msg='flip output is wrong, out =' + str(out_np))
@@ -53,7 +55,10 @@ def test_dygraph(self):
         with fluid.dygraph.guard():
             inputs = fluid.dygraph.to_variable(img)
             ret = paddle.flip(inputs, [0])
-            out_ref = np.array([[4, 5, 6], [1, 2, 3]]).astype(np.float32)
+            ret = ret.flip(0)
+            ret = paddle.flip(ret, 1)
+            out_ref = np.array([[3, 2, 1], [6, 5, 4]]).astype(np.float32)
+
             self.assertTrue(
                 (ret.numpy() == out_ref).all(),
                 msg='flip output is wrong, out =' + str(ret.numpy()))
@@ -82,6 +87,8 @@ def init_test_case(self):
 
     def calc_ref_res(self):
         res = self.inputs['X']
+        if isinstance(self.axis, int):
+            return np.flip(res, self.axis)
         for axis in self.axis:
             res = np.flip(res, axis)
         return res

python/paddle/tensor/manipulation.py

@@ -223,7 +223,7 @@ def flip(x, axis, name=None):
     Args:
         x (Tensor): A Tensor(or LoDTensor) with shape :math:`[N_1, N_2,..., N_k]` . The data type of the input Tensor x
             should be float32, float64, int32, int64, bool.
-        axis (list|tuple): The axis(axes) to flip on. Negative indices for indexing from the end are accepted.
+        axis (list|tuple|int): The axis(axes) to flip on. Negative indices for indexing from the end are accepted.
         name (str, optional): The default value is None.  Normally there is no need for user to set this property.
             For more information, please refer to :ref:`api_guide_Name` .
 
@@ -240,10 +240,17 @@ def flip(x, axis, name=None):
           x = np.arange(image_shape[0] * image_shape[1] * image_shape[2]).reshape(image_shape)
           x = x.astype('float32')
           img = paddle.to_tensor(x)
-          out = paddle.flip(img, [0,1])
+          tmp = paddle.flip(img, [0,1])
+          print(tmp) # [[[10,11],[8, 9]], [[6, 7],[4, 5]], [[2, 3],[0, 1]]]
 
-          print(out) # [[[10,11][8, 9]],[[6, 7],[4, 5]] [[2, 3],[0, 1]]]
+          out = paddle.flip(tmp,-1)
+          print(out) # [[[11,10],[9, 8]], [[7, 6],[5, 4]], [[3, 2],[1, 0]]]
     """
+    if isinstance(axis, int):
+        axis = [axis]
+    if in_dygraph_mode():
+        return core.ops.flip(x, "axis", axis)
+
     helper = LayerHelper("flip", **locals())
     check_type(x, 'X', (Variable), 'flip')
     dtype = helper.input_dtype('x')