update the description words

source/core/CopyInGrid.cpp

@@ -26,7 +26,8 @@
 namespace nts { // namespace nts(NiuTrans.Tensor)
 
 /*
-copy a number of blocks in grid
+copy a number of blocks in grid, 
+i.e., reorder the data blocks in the same memory piece
 >> s - source tensor
 >> t - target tensor
 >> index - index[offset_k + j] means the source block id for the j-th target block

source/core/CopyInGrid.h

@@ -26,7 +26,7 @@
 
 namespace nts { // namespace nts(NiuTrans.Tensor)
 
-/* copy a number of blocks in grid */
+/* copy a number of blocks in grid. i.e., reorder the data blocks in the same memory piece*/
 extern "C"
 void CopyInGrid(XTensor * s, XTensor * t, int * index, int blockDim, int blockNumInGrid, bool isIndexOnDev = false);
 

source/core/CopyIndexed.cpp

@@ -29,7 +29,8 @@ copy indexed sub-tensors
 >> s - the source tensor
 >> t - the target tensor
 >> dim - the leading dimension to define "sub-tensors"
-e.g., for a tensor of size (3, 2, 4) and dim = 2, we have 4 sub-tensors of size (3,2)
+         e.g., for a tensor of size (3, 2, 4) and dim = 2, 
+         we have 4 sub-tensors of size (3,2)
 >> srcIndex - index of the source sub-tensors
 >> indexSize - length of srcIndex (and tgtIndex)
 >> tgtIndex - index of the target sub-tensors