Basic GPU/CUDA test code

gpu_test.cu

#include "timer.h"

/** CUDA libraries */
#include <cuda.h>
#include <helper_cuda.h>

__global__ void kernel () {

}

int main (int argc, char *argv[]) {

    int num = 10000;

    // set & initialize device using command line argument (if any)
    cudaDeviceProp devProp;
    if (argc == 1) {
        // default device id is 0
        checkCudaErrors (cudaSetDevice (0) );
        checkCudaErrors (cudaGetDeviceProperties(&devProp, 0));
    } else {
        // use second argument for number

        // get number of devices
        int num_devices;
        cudaGetDeviceCount(&num_devices);

        // first check if is number
        int id = *(argv[1]) - '0';

        if ((id >= 0) && (id < num_devices)) {
            checkCudaErrors (cudaSetDevice (id) );
        } else {
            // not in range, error
            printf("Error: GPU device number not in correct range\n");
            printf("Provide number between 0 and %i\n", num_devices - 1);
            exit(1);
        }
        checkCudaErrors (cudaGetDeviceProperties(&devProp, id));
    }

    // block and grid dimensions
    dim3 dimBlock ( 1, 1 );
    dim3 dimGrid ( 1, 1 );

    // Allocate device memory
    size_t size = sizeof(int);
    int* y_host;
    y_host = (int *) malloc (size);
    int* y_device;
    cudaMalloc ((void**) &y_device, size);

    //////////////////////////////
    // start timer
    StartTimer();
    //////////////////////////////

    for (int i = 0; i < num; ++i) {
        cudaMemcpy (y_device, y_host, size, cudaMemcpyHostToDevice);
        cudaMemcpy (y_host, y_device, size, cudaMemcpyDeviceToHost);
    }

    /////////////////////////////////
    // end timer
    double runtime = GetTimer();
    /////////////////////////////////

    // convert to sec
    runtime /= 1000.0;
    runtime = 1.0e6 * runtime / ((Real)(num));
    printf("GPU communication latency: %e microseconds\n", runtime);

    return 0;
}