[ADMB Users] Does CUDA suck? answer NO!

[dave fournier]

First there is an error in the code. It should read

            return z;

  and not

           return x+y;

However I thought that maybe the problem is that  addition is too 
trivial compared to the
overhead of moving things to the GPU and back. I changed the function to 
pow(x,y)
and lo!  the el cheapo GPU is faster (about 6 times faster).
So how hard is a vector pow.  All that was necessary was to take the 
included VecAdd
function and modify it to


__global__ void VecPow(const double* A, const double* B, double* C, int N)
{
     int i = blockDim.x * blockIdx.x + threadIdx.x;
     double x=0.0;
     if (i < N)
     {
         C[i] = pow(A[i],B[i]);
     }
}

Code is attached. Note I use mypow just to avoid clash with existing 
admb libs.

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