[GitHub] [incubator-mxnet] roywei commented on a change in pull request #14869: Fix infer shape partial after unknown shape changed to -1

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roywei commented on a change in pull request #14869: Fix infer shape partial after unknown shape changed to -1
URL: https://github.com/apache/incubator-mxnet/pull/14869#discussion_r284847219
 
 

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 File path: src/operator/tensor/dot-inl.h
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 @@ -1207,6 +1207,12 @@ inline bool DotShape(const nnvm::NodeAttrs& attrs,
   CHECK_EQ(out_attrs->size(), 1U);
   mxnet::TShape& lshape = (*in_attrs)[0];
   mxnet::TShape& rshape = (*in_attrs)[1];
+  // return false if lhs and rhs both have fully unknown shape
+  if (!ndim_is_known(lshape) || !ndim_is_known(rshape)) return false;
+  // only partially infer shape if last dim of lhs and first dim of rhs is known
+  bool last_dim_known = dim_size_is_known(lshape, lshape.ndim() > 1 ? lshape.ndim() - 1 : 0);
+  bool first_dim_known = dim_size_is_known(rshape, 0);
 
 Review comment:
   updated the check to:
   lhs ndim > 1, and last dim known
   rhs ndim > 1, and first dim known
   
   but this will silently return false if ndim < -1. 
   We may need more types of checks in addition to `ndim_is_known` and `shape_is_known`. 
   

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