printf inside CUDA __global__ function

Question

I am currently writing a matrix multiplication on a GPU and would like to debug my code, but since I can not use printf inside a device function, is there something else I can do to see what is going on inside that function. This my current function:

__global__ void MatrixMulKernel(Matrix Ad, Matrix Bd, Matrix Xd){      int tx = threadIdx.x;     int ty = threadIdx.y;      int bx = blockIdx.x;     int by = blockIdx.y;      float sum = 0;      for( int k = 0; k < Ad.width ; ++k){         float Melement = Ad.elements[ty * Ad.width + k];         float Nelement = Bd.elements[k * Bd.width + tx];         sum += Melement * Nelement;     }      Xd.elements[ty * Xd.width + tx] = sum; } 

I would love to know if Ad and Bd is what I think it is, and see if that function is actually being called.

Answer 1

CUDA now supports printfs directly in the kernel. For formal description see Appendix B.16 of the CUDA C Programming Guide.