写个opencl c 例程

下面是一个简单的OpenCL C例程，这个例子展示了如何创建一个计算平均值的基本程序。首先假设你已经有一个OpenCL设备和上下文，我们将编写一个函数来计算给定数组的平均值：

#include <stdio.h>
#include <stdlib.h>
#include <cl_platform.h>
#include <cl_device_id.h>
#include <cl_context.h>
#include <cl_command_queue.h>
#include <cl_program.h>
#include <cl_kernel.h>

// OpenCL数据类型
typedef float my_float;

// 求平均值的全局函数
__kernel void average(__global const my_float *input,
                      __global my_float *output,
                      uint32_t num_elements) {
    int gid = get_global_id(0);
    output[gid] = input[gid] / (float)num_elements;
}

void calculate_average(cl_context context, cl_command_queue queue,
                       cl_mem input_buffer, cl_mem output_buffer,
                       size_t global_size, float *host_input_data, float *host_output_data) {
    // 获取全局工作大小
    size_t local_work_size[] = {32};
    cl_int status;

    // 创建平均值 kernel
    const char* kernel_source =
        "__kernel void average(__global const my_float *input, "
        "__global my_float *output, uint32_t num_elements)\n"
        "{\n"
        "    int gid = get_global_id(0);\n"
        "    output[gid] = input[gid] / (float)num_elements;\n"
        "}\n";

    cl_program program = clCreateProgramWithSource(context, 1, &kernel_source, NULL, &status);
    if (status != CL_SUCCESS) {
        printf("Error creating program: %d\n", status);
        return;
    }

    status = clBuildProgram(program, 1, &device_id, "-Dmy_float=float", NULL, NULL);
    if (status != CL_SUCCESS) {
        printf("Error building program: %d\n", status);
        clReleaseProgram(&program);
        return;
    }

    // 创建并编译kernel
    cl_kernel kernel = clCreateKernel(program, "average", &status);
    if (status != CL_SUCCESS) {
        printf("Error creating kernel: %d\n", status);
        clReleaseProgram(&program);
        return;
    }

    // 设置 kernel arguments
    status = clSetKernelArg(kernel, 0, sizeof(input_buffer), &input_buffer);
    status |= clSetKernelArg(kernel, 1, sizeof(output_buffer), &output_buffer);
    status |= clSetKernelArg(kernel, 2, sizeof(uint32_t), &global_size);

    if (status != CL_SUCCESS) {
        printf("Error setting kernel args: %d\n", status);
        clReleaseKernel(&kernel);
        clReleaseProgram(&program);
        return;
    }

    // 分配内存
    size_t global_work_size = global_size;
    size_t local_work_size;
    clEnqueueNDRangeKernel(queue, kernel, 1, NULL, &global_work_size, local_work_size, 0, NULL, NULL);

    // copy结果回主机
    status = clFinish(queue);
    if (status != CL_SUCCESS) {
        printf("Error finishing queue: %d\n", status);
        return;
    }
    cl.enqueue_read_buffer(queue, output_buffer, CL_TRUE, 0, sizeof(my_float) * global_size, host_output_data);

    // 清理资源
    clReleaseKernel(&kernel);
    clReleaseProgram(&program);
}

int main() {
    // ... 初始化OpenCL上下文、队列、设备ID等

    // 从主机分配内存并填充数据
    float *input_host = malloc(sizeof(float) * global_size);
    for (size_t i = 0; i < global_size; ++i)
        input_host[i] = host_input_data[i];

    // 将主机内存转换为设备内存
    cl_mem input_buffer = clCreateBuffer(context, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR, sizeof(float) * global_size, input_host, &status);
    if (status != CL_SUCCESS) {
        printf("Error allocating input buffer: %d\n", status);
        free(input_host);
        return -1;
    }

    // 类似地，创建输出缓冲区
    cl_mem output_buffer = ...; // 你需要创建一个合适的输出缓冲区

    // 调用函数计算平均值
    calculate_average(context, queue, input_buffer, output_buffer, global_size, input_host, host_output_data);

    // 清理
    clReleaseMemObject(input_buffer);
    free(input_host);
    return 0;
}

这只是一个基础示例，实际应用可能需要处理更多的错误情况和更复杂的任务。记得在main函数结束时释放所有OpenCL资源。