Question

When calling the function cudaMemcpyToSymbol, I get Invalid value error (cudaErrorInvalidValue). The code where the error occurs is something like this.

__constant__ int c_queryLength; //Length of query sequence in chunks of 4
...............
if((cuda_err = cudaMemcpyToSymbol(c_queryLength,&queryLengthInChunks,
  sizeof(queryLengthInChunks),0, cudaMemcpyHostToDevice))!=cudaSuccess)
{
 // Check which error occured;
 ...............
}

Here the value of queryLengthInChunks, which is of type size_t, is 36. Why am I getting this error. Any possible reasons for that?

Answer 1

You need to check whether size_t is the same size as int on your system. If size_t is 8 bytes and int is only 4 bytes then the call will fail – you can’t just copy an 8 byte variable to a 4 byte CUDA device constant.