fix replicate pad when input size is 0 (#36510)

* fix replicate pad when input size is 0
* add unit test

paddle/fluid/operators/pad3d_op.cc

@@ -565,13 +565,11 @@ class Pad3dCPUKernel : public framework::OpKernel<T> {
                             " in reflect mode"
                             ", but received depth(%d) and pad_right(%d).",
                             in_width, pads[1]));
-    }
-
-    if (mode == "circular") {
-      PADDLE_ENFORCE_NE(
-          in_depth * in_height * in_width, 0,
-          platform::errors::InvalidArgument(
-              "The input tensor size can not be 0 for circular padding mode."));
+    } else if (mode == "circular" || mode == "replicate") {
+      PADDLE_ENFORCE_NE(in_depth * in_height * in_width, 0,
+                        platform::errors::InvalidArgument(
+                            "The input tensor size can not be 0 for circular "
+                            "or replicate padding mode."));
     }
 
     const int pad_left = pads[0];

paddle/fluid/operators/pad3d_op.cu

@@ -618,13 +618,11 @@ class Pad3dCUDAKernel : public framework::OpKernel<T> {
                             " in reflect mode"
                             ", but received depth(%d) and pad_right(%d).",
                             in_width, pads[1]));
-    }
-
-    if (mode == "circular") {
-      PADDLE_ENFORCE_NE(
-          in_depth * in_height * in_width, 0,
-          platform::errors::InvalidArgument(
-              "The input tensor size can not be 0 for circular padding mode."));
+    } else if (mode == "circular" || mode == "replicate") {
+      PADDLE_ENFORCE_NE(in_depth * in_height * in_width, 0,
+                        platform::errors::InvalidArgument(
+                            "The input tensor size can not be 0 for circular "
+                            "or replicate padding mode."));
     }
 
     const int pad_left = pads[0];

python/paddle/fluid/tests/unittests/test_pad3d_op.py

@@ -732,6 +732,15 @@ class TestPad3dOpError(unittest.TestCase):
                       mode='circular',
                       data_format="NCDHW")
 
+        def test_replicate_1():
+            input_shape = (1, 2, 0, 4, 5)
+            data = np.random.rand(*input_shape).astype(np.float32)
+            x = paddle.to_tensor(data)
+            y = F.pad(x,
+                      pad=[1, 1, 1, 1, 2, 3],
+                      mode='replicate',
+                      data_format="NCDHW")
+
         paddle.disable_static()
         for place in self.places:
             self.assertRaises(ValueError, test_variable)
@@ -739,6 +748,7 @@ class TestPad3dOpError(unittest.TestCase):
             self.assertRaises(Exception, test_reflect_2)
             self.assertRaises(Exception, test_reflect_3)
             self.assertRaises(Exception, test_circular_1)
+            self.assertRaises(Exception, test_replicate_1)
         paddle.enable_static()