szha commented on a change in pull request #7772: Use memcopy instead of
assigning each individual element
URL: https://github.com/apache/incubator-mxnet/pull/7772#discussion_r137418825
##########
File path: src/operator/tensor/cast_storage-inl.h
##########
@@ -120,9 +119,7 @@ struct CastStorageRspDnsKernel {
IType rid = idx[i];
dim_t dns_offset = rid * row_length;
dim_t rsp_offset = i * row_length;
- for (dim_t col = 0; col < row_length; col++) {
- dns[dns_offset + col] = data[rsp_offset + col];
- }
+ memcpy(dns + dns_offset, data + rsp_offset, sizeof(DType) * row_length);
Review comment:
Did a bit of searching on this and the following turns up:
1. memcpy seems to work in
https://stackoverflow.com/questions/10456728/is-there-an-equivalent-to-memcpy-that-works-inside-a-cuda-kernel
(might be outdated)
2. cudaMemcpyAsync on device is available since CUDA6, though there are
[limitations](http://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#ixzz4rwhsHEfu)
```
Notes about all memcpy/memset functions:
Only async memcpy/set functions are supported
Only device-to-device memcpy is permitted
May not pass in local or shared memory pointers
```
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