How to return a single variable from a CUDA kernel function?

Question

I have a CUDA search function which calculate one single variable. How can I return it back.

__global__ 
void G_SearchByNameID(node* Node, long nodeCount, long s         


        

Answer 1

I've been using __device__ variables for this purpose, that way you don't have to bother with cudaMalloc and cudaFree and you don't have to pass a pointer as a kernel argument, which saves you a register in your kernel to boot.

__device__ long d_answer;

__global__ void G_SearchByNameID() {
  d_answer = 2;
}

int main() {
  SearchByNameID<<<1,1>>>();
  typeof(d_answer) answer;
  cudaMemcpyFromSymbol(&answer, "d_answer", sizeof(answer), 0, cudaMemcpyDeviceToHost);
  printf("answer: %d\n", answer);
  return 0;
}