如何在openCL中运行hello world程序？

#include <stdio.h>
#include <CL/cl.h>

int main() {
    cl_platform_id platform;
    cl_device_id device;
    cl_context context;
    cl_command_queue queue;
    cl_program program;
    cl_kernel kernel;
    cl_mem memobj;
    cl_int err;

    // 获取平台
    err = clGetPlatformIDs(1, &platform, NULL);

    // 获取设备
    err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_GPU, 1, &device, NULL);

    // 创建上下文
    context = clCreateContext(NULL, 1, &device, NULL, NULL, &err);

    // 创建命令队列
    queue = clCreateCommandQueue(context, device, 0, &err);

    // 创建内存对象
    memobj = clCreateBuffer(context, CL_MEM_READ_WRITE, sizeof(char) * 12, NULL, &err);

    // 构建内核程序
    const char* source = "__kernel void hello_world(__global char* buffer) { buffer[0] = 'H'; buffer[1] = 'e'; buffer[2] = 'l'; buffer[3] = 'l'; buffer[4] = 'o'; buffer[5] = ' '; buffer[6] = 'W'; buffer[7] = 'o'; buffer[8] = 'r'; buffer[9] = 'l'; buffer[10] = 'd'; buffer[11] = '\\0'; }";
    program = clCreateProgramWithSource(context, 1, &source, NULL, &err);
    err = clBuildProgram(program, 1, &device, NULL, NULL, NULL);

    // 创建内核
    kernel = clCreateKernel(program, "hello_world", &err);

    // 设置内核参数
    err = clSetKernelArg(kernel, 0, sizeof(cl_mem), (void*)&memobj);

    // 执行内核
    size_t global_item_size = 1;
    size_t local_item_size = 1;
    err = clEnqueueNDRangeKernel(queue, kernel, 1, NULL, &global_item_size, &local_item_size, 0, NULL, NULL);

    // 读取结果
    char result[12];
    err = clEnqueueReadBuffer(queue, memobj, CL_TRUE, 0, sizeof(char) * 12, result, 0, NULL, NULL);

    // 输出结果
    printf("%s\n", result);

    // 释放资源
    err = clReleaseMemObject(memobj);
    err = clReleaseKernel(kernel);
    err = clReleaseProgram(program);
    err = clReleaseCommandQueue(queue);
    err = clReleaseContext(context);

    return 0;
}

gcc -o hello_world hello_world.c -lOpenCL

./hello_world