supplement the function of slice

Author: hbwx24

python/paddle/fluid/tests/unittests/dygraph_to_static/test_slice.py

@@ -18,6 +18,7 @@
 import numpy as np
 
 import paddle
+from paddle.static import InputSpec
 
 SEED = 2020
 np.random.seed(SEED)
@@ -176,5 +177,44 @@ def test_set_value_with_save(self):
             output_spec=None)
 
 
+class TestSliceSupplementCase(unittest.TestCase):
+    def test_static_slice_step(self):
+        paddle.enable_static()
+        array = np.arange(4**3).reshape((4, 4, 4))
+
+        x = paddle.static.data(name='x', shape=[4, 4, 4], dtype='int64')
+        z1 = x[::2]
+        z2 = x[::-2]
+
+        place = paddle.CPUPlace()
+        prog = paddle.static.default_main_program()
+        exe = paddle.static.Executor(place)
+        exe.run(paddle.static.default_startup_program())
+
+        out = exe.run(prog, feed={'x': array}, fetch_list=[z1, z2])
+
+        self.assertTrue(np.array_equal(out[0], array[::2]))
+        self.assertTrue(np.array_equal(out[1], array[::-2]))
+
+    def test_static_slice_step_dygraph2static(self):
+        paddle.disable_static()
+
+        array = np.arange(4**2 * 5).reshape((5, 4, 4))
+        inps = paddle.to_tensor(array)
+
+        def func(inps):
+            return inps[::2], inps[::-2]
+
+        origin_result = func(inps)
+        sfunc = paddle.jit.to_static(
+            func, input_spec=[InputSpec(shape=[None, 4, 4])])
+        static_result = sfunc(inps)
+
+        self.assertTrue(
+            np.array_equal(origin_result[0].numpy(), static_result[0].numpy()))
+        self.assertTrue(
+            np.array_equal(origin_result[1].numpy(), static_result[1].numpy()))
+
+
 if __name__ == '__main__':
     unittest.main()

python/paddle/fluid/variable_index.py

@@ -144,13 +144,14 @@ def _getitem_impl_(var, item):
 
             step = 1 if step is None else step
 
-            if start is None and end is None:
-                assert (step == -1)
+            if start is None and end is None and step == -1:
                 reverse_axes.append(dim)
                 continue
 
-            start = 0 if start is None else start
-            end = MAX_INTEGER if end is None else end
+            if start is None:
+                start = 0 if step > 0 else MAX_INTEGER
+            if end is None:
+                end = MAX_INTEGER if step > 0 else 0
 
         elif isinstance(slice_item, list):
             is_bool_list = False