[GitHub] cjolivier01 commented on a change in pull request #8566: optimize broadcast

[GitBox <gi...@apache.org>]

cjolivier01 commented on a change in pull request #8566: optimize broadcast
URL: https://github.com/apache/incubator-mxnet/pull/8566#discussion_r149239749
 
 

 ##########
 File path: src/operator/mxnet_op.h
 ##########
 @@ -199,6 +199,37 @@ MSHADOW_XINLINE Shape<ndim> calc_stride(const Shape<ndim>& shape) {
   return stride;
 }
 
+/* Increment coordinates and modify index */
+template<int ndim>
+MSHADOW_XINLINE void inc(Shape<ndim>* coord, const Shape<ndim>& shape,
+                         index_t* idx, const Shape<ndim>& stride) {
+  ++(*coord)[ndim-1];
+  *idx += stride[ndim-1];
+  #pragma unroll
+  for (int i = ndim - 1; i > 0 && (*coord)[i] >= shape[i]; --i) {
+    (*coord)[i] -= shape[i];
+    ++(*coord)[i-1];
+    *idx = *idx + stride[i-1] - shape[i] * stride[i];
 
 Review comment:
   curious: why not += ?

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