Question

我对使用OpenCL映射缓冲区的代码是否正确感到困惑。

我已经了解缓冲区/地图特定操作是在OpenCL环境中使用GPU映射（零拷贝）内存机制的最有效方法。

我不明白为什么res_nb在每次迭代时都没有初始化为0。在每次迭代时，res_nb乘以2

我知道我应该做错误检查等等。

OpenCL代码

__kernel void test(
    __global uint* res_nb_g,
)
{
    // atomicAdd will return the value which was stored at "res_nb_g" before "1" was added.
    int i = atomic_add(res_nb_g, 1);
}

C代码

cl_uint res_nb = 0;

cl_mem res_nb_g = clCreateBuffer(context, CL_MEM_READ_ONLY | CL_MEM_ALLOC_HOST_PTR | CL_MEM_COPY_HOST_PTR, sizeof(cl_uint), &res_nb, &clStatus);

clSetKernelArg(test_kernel, 0, sizeof(res_nb_g), &res_nb_g);

for (int run = 0; run < 10; run++) {
    res_nb = *((cl_uint *)clEnqueueMapBuffer(clqueue, res_nb_g, CL_TRUE, CL_MAP_WRITE, 0, sizeof(cl_uint), 0, NULL, NULL, NULL));
    res_nb = 0;
    clEnqueueUnmapMemObject(clqueue, res_nb_g, &res_nb, 0, NULL, NULL);

    clEnqueueNDRangeKernel(clqueue, test_kernel, 1, NULL, &g_work_size, &l_work_size, 0, NULL, NULL);

    clFinish(clqueue);

    res_nb = *((cl_uint *)clEnqueueMapBuffer(clqueue, res_nb_g, CL_TRUE, CL_MAP_READ, 0, sizeof(cl_uint), 0, NULL, NULL, &clStatus));
}

使用我的解决方案进行编辑：

    cl_uint *res_nb = 0;
    cl_mem res_nb_g = clCreateBuffer(context, CL_MEM_READ_WRITE | CL_MEM_ALLOC_HOST_PTR, sizeof(cl_uint), NULL, &clStatus);
    clCheckError(clStatus);

    clStatus = clSetKernelArg(test_kernel, 0, sizeof(res_nb_g), &res_nb_g);
    clCheckError(clStatus);

    for (cl_uint run = 0; run < nbruns; run++) {
        res_nb = (cl_uint *)clEnqueueMapBuffer(clqueue, res_nb_g, CL_TRUE, CL_MAP_WRITE, 0, sizeof(cl_uint), 0, NULL, NULL, &clStatus);
        clCheckError(clStatus);
        *res_nb = 0;
        clStatus = clEnqueueUnmapMemObject(clqueue, res_nb_g, res_nb, 0, NULL, NULL);
        clCheckError(clStatus);

        clStatus = clEnqueueNDRangeKernel(clqueue, test_kernel, 1, NULL, &g_work_size, &l_work_size, 0, NULL, NULL);
        clCheckError(clStatus);

        clFinish(clqueue); // Not necessary

        res_nb = (cl_uint *)clEnqueueMapBuffer(clqueue, res_nb_g, CL_TRUE, CL_MAP_READ, 0, sizeof(cl_uint), 0, NULL, NULL, &clStatus);
        clCheckError(clStatus);
        // Edit: remark @ Andrew Savonichev
        clStatus = clEnqueueUnmapMemObject(clqueue, res_nb_g, res_nb, 0, NULL, NULL);
        clCheckError(clStatus);
    }

如何在OpenCL中使用缓冲区分配和映射内存机制？

0 个答案: