Retaining dot product on GPGPU using CUBLAS routine

Question

I am writing a code to compute dot product of two vectors using CUBLAS routine of dot product but it returns the value in host memory. I want to use the dot product for furt

Answer 1

You can do this in CUBLAS as long as you use the "V2" API. The newer API includes a function cublasSetPointerMode which you can use to set the API to assume that all routines which return a scalar value will be passed a device pointer rather than a host pointer. This is discussed in Section 2.4 of the latest CUBLAS documentation. For example:

#include 
#include 
#include 

int main(void)
{
    const int nvals = 10;
    const size_t sz = sizeof(double) * (size_t)nvals;
    double x[nvals], y[nvals];
    double *x_, *y_, *result_;
    double result=0., resulth=0.;

    for(int i=0; i

Using CUBLAS_POINTER_MODE_DEVICE makes cublasDdot assume that result_ is a device pointer, and there is no attempt made to copy the result back to the host. Note that this makes routines like dot asynchronous, so you might need to keep on eye on synchronization between device and host.