[DOC] Add doc for maybe_wrap_dim (#63161)

Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/63161

Test Plan: Imported from OSS

Reviewed By: pbelevich

Differential Revision: D30629451

Pulled By: tugsbayasgalan

fbshipit-source-id: b03f030f197e10393a8ff223b240d23c30858028

diff --git a/aten/src/ATen/WrapDimUtils.h b/aten/src/ATen/WrapDimUtils.h
index 2768efe..13e605c 100644 (file)
--- a/aten/src/ATen/WrapDimUtils.h
+++ b/aten/src/ATen/WrapDimUtils.h
@@ -7,6 +7,9 @@
 namespace at {
 
 static inline int64_t maybe_wrap_dim(int64_t dim, int64_t dim_post_expr, bool wrap_scalar=true) {
+  // if dim_post_expr is 0 and wrap_scalar is true, then dim must be in the range [-1, 0].
+  // This is a special case for scalar tensors and manifests in e.g. torch.sum(scalar_tensor, 0)
+  // Otherwise, dim should be in the range [-dim_post_expr, dim_post_expr-1].
   return c10::maybe_wrap_dim(dim, dim_post_expr, wrap_scalar);
 }