Zero slice bug (#20914)

Brennan Vincent · facebook-github-bot · commit c46c6a4fe68a · 2019-05-24T15:10:59.000-07:00
Summary: Bug reported internally at FB: ```python >>> t=torch.from_numpy(np.empty((0,4))) >>> t[:,1::2]*=1 Traceback (most recent call last): File "<stdin>", line 1, in <module> RuntimeError: Trying to resize storage that is not resizable at ../aten/src/TH/THStorageFunctions.cpp:76 ``` This happens because the storage offset of `t[:, 1::2]` is 1, and it has 0 elements. We can fix this by avoiding resizing the storage for no-element arrays. (We could *also* have avoided it by not modifying the storage index in this case, but I felt this way was more semantically correct -- in general, we should not be assuming it's okay to do anything to the storage when it has zero elements). Pull Request resolved: #20914 Differential Revision: D15497860 Pulled By: umanwizard fbshipit-source-id: 6af61d73a05edfc5c07ce8be9e530f15bf72e6a9
diff --git a/aten/src/ATen/native/Resize.h b/aten/src/ATen/native/Resize.h
@@ -10,7 +10,12 @@ namespace at { namespace native {
 // to benchmark than TH; I can't get gbenchmark to call fns from THTensor.cpp
 
 static inline void maybe_resize_storage_cpu(TensorImpl* self, int64_t new_size) {
-  if (new_size + self->storage_offset() > 0) {
+  // It does not make sense to try to resize a storage
+  // to hold 0 elements, and this can break
+  // if storage_offset is positive but
+  // new_size is 0, so just bail in that case
+  // (same comment is in Resize.cuh)
+  if (new_size > 0) {
     if (!THTensor_getStoragePtr(self)) {
       THTensor_stealAndSetStoragePtr(self, THStorage_new(self->dtype()));
     }
diff --git a/aten/src/ATen/native/cuda/Resize.cuh b/aten/src/ATen/native/cuda/Resize.cuh
@@ -12,7 +12,12 @@ namespace at { namespace native {
 // to benchmark than THC; I can't get gbenchmark to call fns from THTensor.cpp
 
 static inline void maybe_resize_storage_cuda(TensorImpl* self, int64_t new_size) {
-  if (new_size + self->storage_offset() > 0) {
+  // It does not make sense to try to resize a storage
+  // to hold 0 elements, and this can break
+  // if storage_offset is positive but
+  // new_size is 0, so just bail in that case
+  // (same comment is in Resize.h)
+  if (new_size > 0) {
     if (!THTensor_getStoragePtr(self)) {
       AT_ERROR("Tensor: invalid null storage");
     }
diff --git a/test/test_torch.py b/test/test_torch.py
@@ -7328,6 +7328,14 @@ def _test_advancedindex_big(self, conv_fn):
     def test_advancedindex_big(self):
         self._test_advancedindex_big(self, lambda x: x)
 
+    @unittest.skipIf(not TEST_NUMPY, "Numpy not found")
+    def test_empty_storage_view(self):
+        # we should be able to "modify" slices of a 0-element
+        # array without an error being raised due to
+        # trying to resize its storage
+        t = torch.from_numpy(np.empty((0, 4)))
+        t[:, 1::2] *= 1
+
     @unittest.skipIf(not TEST_NUMPY, "Numpy not found")
     def test_newaxis_numpy_comparison(self):
         def run_test(tensor, *idx):
