cuda vector addition

http://webgpu.hwu.crhc.illinois.edu/

// MP 1
#include    <wb.h>

__global__ void vecAdd(float * in1, float * in2, float * out, int len) {
    //@@ Insert code to implement vector addition here
    int i = blockIdx.x * blockDim.x + threadIdx.x ; 
    if( i < len )
        out[i] = in1[i] + in2[i] ; 
}

int main(int argc, char ** argv) {
    wbArg_t args;
    int inputLength;
    float * hostInput1;
    float * hostInput2;
    float * hostOutput;
    float * deviceInput1;
    float * deviceInput2;
    float * deviceOutput;

    args = wbArg_read(argc, argv);

    wbTime_start(Generic, "Importing data and creating memory on host");
    hostInput1 = (float *) wbImport(wbArg_getInputFile(args, 0), &inputLength);
    hostInput2 = (float *) wbImport(wbArg_getInputFile(args, 1), &inputLength);
    hostOutput = (float *) malloc(inputLength * sizeof(float));
    wbTime_stop(Generic, "Importing data and creating memory on host");

    wbLog(TRACE, "The input length is ", inputLength);

    wbTime_start(GPU, "Allocating GPU memory.");
    //@@ Allocate GPU memory here
    
    cudaMalloc((void**)&deviceInput1 , sizeof(float) * inputLength);
    cudaMalloc((void**)&deviceInput2 , sizeof(float) * inputLength);
    cudaMalloc((void**)&deviceOutput , sizeof(float) * inputLength);
    
    
    wbTime_stop(GPU, "Allocating GPU memory.");
    
    wbTime_start(GPU, "Copying input memory to the GPU.");
    //@@ Copy memory to the GPU here
    cudaMemcpy(deviceInput1,hostInput1,sizeof(float) * inputLength , cudaMemcpyHostToDevice) ;
    cudaMemcpy(deviceInput2,hostInput2,sizeof(float) * inputLength , cudaMemcpyHostToDevice) ; 
    

    wbTime_stop(GPU, "Copying input memory to the GPU.");
    
    //@@ Initialize the grid and block dimensions here
    
    
    dim3 DimGrid( (inputLength  - 1)/ 256 + 1 , 1 , 1 ) ;
    dim3 DimBlock( 256 ,1 ,1 ) ; 
    
    
    
    wbTime_start(Compute, "Performing CUDA computation");
    //@@ Launch the GPU Kernel here
    
    vecAdd<<<DimGrid,DimBlock>>>(deviceInput1,deviceInput2,deviceOutput,inputLength);
    

    cudaThreadSynchronize();
    wbTime_stop(Compute, "Performing CUDA computation");
    
    wbTime_start(Copy, "Copying output memory to the CPU");
    //@@ Copy the GPU memory back to the CPU here
    
    cudaMemcpy(hostOutput,deviceOutput,sizeof(float)*inputLength,cudaMemcpyDeviceToHost);
    

    wbTime_stop(Copy, "Copying output memory to the CPU");

    wbTime_start(GPU, "Freeing GPU Memory");
    //@@ Free the GPU memory here
    
    cudaFree(deviceInput1);
    cudaFree(deviceInput2);
    cudaFree(deviceOutput);


    wbTime_stop(GPU, "Freeing GPU Memory");

    wbSolution(args, hostOutput, inputLength);

    free(hostInput1);
    free(hostInput2);
    free(hostOutput);

    return 0;
}