#include "cuda_runtime.h"
#include "device_launch_parameters.h"

#include <stdio.h>
__global__ void gpuAdd(int *d_a, int *d_b, int *d_c) {
	*d_c = *d_a + *d_b;
}
int main()
{
	//Defining host variables
	int h_a, h_b, h_c;
	//Defining Device Pointers
	int *d_a, *d_b, *d_c;
	//Initializing host variables
	h_a = 1;
	h_b = 4;

    
    cudaError_t cudaStatus;
	  

    // Allocate GPU buffers for three vectors (two input, one output)    .
    cudaStatus = cudaMalloc((void**)&d_c, sizeof(int));
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMalloc failed!");
        goto Error;
    }
	cudaStatus = cudaMalloc((void**)&d_a, sizeof(int));
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMalloc failed!");
        goto Error;
    }

    cudaStatus = cudaMalloc((void**)&d_b, sizeof(int));
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMalloc failed!");
        goto Error;
    }

    // Copy input vectors from host memory to GPU buffers.
    cudaStatus = cudaMemcpy(d_a,&h_a, sizeof(int), cudaMemcpyHostToDevice);
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMemcpy failed!");
        goto Error;
    }

    cudaStatus = cudaMemcpy(d_b, &h_b, sizeof(int), cudaMemcpyHostToDevice);
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMemcpy failed!");
        goto Error;
    }

    // Launch a kernel on the GPU with one thread for each element.
    gpuAdd<<<1, 1>>>(d_a, d_b, d_c);

    // Check for any errors launching the kernel
    cudaStatus = cudaGetLastError();
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "addKernel launch failed: %s\n", cudaGetErrorString(cudaStatus));
        goto Error;
    }
    
    // Copy output vector from GPU buffer to host memory.
    cudaStatus = cudaMemcpy(&h_c, d_c, sizeof(int), cudaMemcpyDeviceToHost);
    if (cudaStatus != cudaSuccess) {
        fprintf(stderr, "cudaMemcpy failed!");
        goto Error;
    }
	printf("Passing Parameter by Reference Output: %d + %d = %d\n", h_a, h_b, h_c);
Error:
    cudaFree(d_c);
    cudaFree(d_a);
    cudaFree(d_b);
    
    return 0;
}