inc_vector.c

/*
Increment a vector, one value per work item.

It is useless to do this on a GPU, not enough work / IO,
it's just a clEnqueueNDRangeKernel + get_global_id hello world.

- http://stackoverflow.com/questions/15194798/vector-step-addition-slower-on-cuda
- http://stackoverflow.com/questions/22005405/how-to-add-up-the-elements-of-an-array-in-gpu-any-function-similar-to-cublasdas
- http://stackoverflow.com/questions/15161575/reduction-for-sum-of-vector-when-size-is-not-power-of-2
*/

#include "common.h"

int main(void) {
    const char *source =
        "__kernel void kmain(__global int *out) {\n"
        "    out[get_global_id(0)]++;\n"
        "}\n"
    ;
    cl_int input[] = {1, 2};
    cl_mem buffer;
    Common common;
    const size_t global_work_size = sizeof(input) / sizeof(input[0]);

    /* Run kernel. */
    common_init(&common, source);
    buffer = clCreateBuffer(common.context, CL_MEM_READ_WRITE | CL_MEM_COPY_HOST_PTR, sizeof(input), input, NULL);
    clSetKernelArg(common.kernel, 0, sizeof(buffer), &buffer);
    clEnqueueNDRangeKernel(common.command_queue, common.kernel, 1, NULL, &global_work_size, NULL, 0, NULL, NULL);
    clFlush(common.command_queue);
    clFinish(common.command_queue);
    clEnqueueReadBuffer(common.command_queue, buffer, CL_TRUE, 0, sizeof(input), input, 0, NULL, NULL);

    /* Assertions. */
    assert(input[0] == 2);
    assert(input[1] == 3);

    /* Cleanup. */
    clReleaseMemObject(buffer);
    common_deinit(&common);
    return EXIT_SUCCESS;
}