Fix int32 overflow in SummaryOps.cu getBin #25747 (#25748)
Summary:
Fixes issue https://github.com/pytorch/pytorch/issues/25747 by upcasting to int64 before multiplication. Should be good enough for all reasonable nbins
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25748
Differential Revision: D17269111
Pulled By: ezyang
fbshipit-source-id: 484be39080571203264a1bb9898ecf23d1aeafab
