fix the bug in nni/compression/pytorch/speedup/infer_shape.py, line n…

…o. 625-626 (#3588)

nni/compression/pytorch/speedup/infer_shape.py

@@ -597,15 +597,15 @@ def view_outshape(module_masks, mask, shape):
     Parameters
     ----------
     module_masks : ModuleMasks
-        The ModuleMasks instance of the ```flatten``` op
+        The ModuleMasks instance of the ```view``` op
     mask : CoarseMask
-        The mask of its input tensor
+        The mask of its output tensor
     shape : dict
         Original shape of its input and output tensors
     Returns
     -------
     CoarseMask
-        The mask of its output tensor
+        The mask of its input tensor
     """
     # NOTE: the case constrained by the following four asserts
     assert shape['in_shape'][0] == shape['out_shape'][0]
@@ -620,10 +620,11 @@ def view_outshape(module_masks, mask, shape):
 
     module_masks.set_output_mask(mask)
     input_cmask = CoarseMask(num_dim=4)
-    index = []
+    index = set()
     step_size = shape['in_shape'][2] * shape['in_shape'][3]
     for loc in mask.mask_index[1]:
-        index.extend([loc * step_size + i for i in range(step_size)])
+        index.add(loc // step_size)
+    index = sorted(list(index))
     input_cmask.add_index_mask(dim=1, index=torch.tensor(index).to(mask.mask_index[1].device))  # pylint: disable=not-callable
     module_masks.set_input_mask(input_cmask)