fix norrow_copy correctness issue for non-contiguous input for cpu path (#91789)

XiaobingSuper · pytorchmergebot · commit 136dadd68998 · 2023-01-09T00:55:03.000Z
Fix #91690. Pull Request resolved: #91789 Approved by: https://github.com/jgong5, https://github.com/lezcano
diff --git a/aten/src/ATen/native/TensorShape.cpp b/aten/src/ATen/native/TensorShape.cpp
@@ -1217,7 +1217,7 @@ Tensor narrow_copy_dense(const Tensor& self, int64_t dim, int64_t start, int64_t
 // Should just use narrow_copy_out, but this API is used internally at Meta:
 // https://github.com/pytorch/pytorch/pull/87045#issuecomment-1309353561
 Tensor narrow_copy_dense_cpu(const Tensor& self, int64_t dim, int64_t start, int64_t length){
-  auto output = at::empty_like(self);
+  auto output = at::empty({0}, self.options());
   return narrow_copy_dense_cpu_out(self, dim, start, length, output);
 }
 
diff --git a/test/test_torch.py b/test/test_torch.py
@@ -2971,6 +2971,13 @@ def test_narrow_empty(self, device):
             sz[d] = 0
             self.assertEqual(sz, y.size())
 
+    def test_narrow_copy_non_contiguous(self, device):
+        # see https://github.com/pytorch/pytorch/issues/91690.
+        inp = torch.randn(10, 2, device=device).movedim(-1, 0)
+        expected = torch.narrow_copy(inp.contiguous(), 1, 0, 10)
+        actual = torch.narrow_copy(inp, 1, 0, 10)
+        self.assertEqual(expected, actual)
+
     # FIXME: move to indexing test suite
     @parametrize("reduce", ['prod', 'amin', 'amax', 'mean'])
     @dtypes(*all_types_and(torch.half, torch.bfloat16))

Original file line number	Diff line number	Diff line change
`@@ -1217,7 +1217,7 @@ Tensor narrow_copy_dense(const Tensor& self, int64_t dim, int64_t start, int64_t`
`1217`	`1217`	`// Should just use narrow_copy_out, but this API is used internally at Meta:`
`1218`	`1218`	`// https://github.com/pytorch/pytorch/pull/87045#issuecomment-1309353561`
`1219`	`1219`	`Tensor narrow_copy_dense_cpu(const Tensor& self, int64_t dim, int64_t start, int64_t length){`
`1220`		`- auto output = at::empty_like(self);`
	`1220`	`+ auto output = at::empty({0}, self.options());`
`1221`	`1221`	`return narrow_copy_dense_cpu_out(self, dim, start, length, output);`
`1222`	`1222`	`}`
`1223`	`1223`