vector addition using CUDA API

cuda-vec_add.cu

/* File:     vec_add.cu
 * Purpose:  Implement vector addition on a gpu using cuda
 *
 * Compile:  nvcc [-g] [-G] -o vec_add vec_add.cu
 * Run:      ./vec_add
 */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <math.h>

__global__ void Vec_add(float x[], float y[], float z[], int n) {
    int thread_id = threadIdx.x;
    if (thread_id < n){
        z[thread_id] = x[thread_id] + y[thread_id];
    }
}


int main(int argc, char* argv[]) {
    int n, m;
    float *h_x, *h_y, *h_z;
    float *d_x, *d_y, *d_z;
    size_t size;

    /* Define vector length */
    n = 1000;
    m = 20;
    size = n*sizeof(float);

    // Allocate memory for the vectors on host memory.
    h_x = (float*) malloc(size);
    h_y = (float*) malloc(size);
    h_z = (float*) malloc(size);

    for (int i = 0; i < n; i++) {
        h_x[i] = i+1;
        h_y[i] = n-i;
    }

    // Print original vectors.
    printf("h_x = ");
    for (int i = 0; i < m; i++){
        printf("%.1f ", h_x[i]);
    }
    printf("\n\n");
    printf("h_y = ");
    for (int i = 0; i < m; i++){
        printf("%.1f ", h_y[i]);
    }
    printf("\n\n");


    /* Allocate vectors in device memory */
    cudaMalloc(&d_x, size);
    cudaMalloc(&d_y, size);
    cudaMalloc(&d_z, size);

    /* Copy vectors from host memory to device memory */
    cudaMemcpy(d_x, h_x, size, cudaMemcpyHostToDevice);
    cudaMemcpy(d_y, h_y, size, cudaMemcpyHostToDevice);
    
    /* Kernel Call */
    Vec_add<<<1,1000>>>(d_x, d_y, d_z, n);

    cudaThreadSynchronize();
    cudaMemcpy(h_z, d_z, size, cudaMemcpyDeviceToHost);
    printf("The sum is: \n");
    for (int i = 0; i < m; i++){
        printf("%.1f ", h_z[i]);
    }
    printf("\n");


    /* Free device memory */
    cudaFree(d_x);
    cudaFree(d_y);
    cudaFree(d_z);
    /* Free host memory */
    free(h_x);
    free(h_y);
    free(h_z);

    return 0;
}  /* main */