windows下如何安装OpenCL

安装OpenCL可以使你的电脑更好地支持并行计算、图形处理、机器学习等任务。以下是Windows下安装OpenCL的完整攻略。

一、检查显卡是否支持OpenCL

在安装OpenCL之前，需要确保你的显卡支持OpenCL。可以在显卡厂商的官网上查找相关信息，或者使用GPU-Z、Speccy等工具检查显卡信息。

二、下载OpenCL驱动程序

下载对应的OpenCL驱动程序，通常可以在显卡厂商的官网上找到。例如，NVIDIA的OpenCL驱动程序可以在其官网的“驱动程序下载”页面找到。

三、安装OpenCL驱动程序

双击下载的OpenCL驱动程序安装包，按照提示完成安装。在安装过程中，可能需要重启电脑。

四、安装OpenCL SDK

如果需要开发OpenCL应用程序，则需要安装OpenCL SDK。常见的OpenCL SDK有AMD APP SDK和Intel SDK for OpenCL Applications，可以在它们的官网上下载安装包。

五、测试OpenCL是否安装成功

可以通过运行一个简单的OpenCL程序测试是否安装成功。以下给出两个示例：

示例一：使用OpenCL计算圆周率

新建一个文本文件，输入以下代码：

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

#define M_PI 3.14159265358979323846

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 pi_buffer;
    cl_int err;

    // Step 1: Discover hardware
    err = clGetPlatformIDs(1, &platform, NULL);
    err = clGetDeviceIDs(platform, CL_DEVICE_TYPE_GPU, 1, &device, NULL);

    // Step 2: Create context
    context = clCreateContext(NULL, 1, &device, NULL, NULL, &err);

    // Step 3: Create command queue
    queue = clCreateCommandQueue(context, device, 0, &err);

    // Step 4: Create program from binary
    const char *source = "__kernel void calc_pi(__global float *pi)\n"
                         "{\n"
                         "    const size_t i = get_global_id(0);\n"
                         "    const float x = (i + 0.5f) / (float)get_global_size(0);\n"
                         "    pi[i] = 4.0f / (1.0f + x*x);\n"
                         "}\n";
    program = clCreateProgramWithSource(context, 1, &source, NULL, &err);
    err = clBuildProgram(program, 1, &device, NULL, NULL, NULL);

    // Step 5: Create kernel
    kernel = clCreateKernel(program, "calc_pi", &err);

    // Step 6: Allocate memory on device
    pi_buffer = clCreateBuffer(context, CL_MEM_WRITE_ONLY, sizeof(float)*1024, NULL, &err);

    // Step 7: Set kernel arguments
    err = clSetKernelArg(kernel, 0, sizeof(pi_buffer), &pi_buffer);

    // Step 8: Execute kernel
    size_t global_work_size[1] = { 1024 };
    err = clEnqueueNDRangeKernel(queue, kernel, 1, NULL, global_work_size, NULL, 0, NULL, NULL);

    // Step 9: Copy result from device to host
    float pi[1024];
    err = clEnqueueReadBuffer(queue, pi_buffer, CL_TRUE, 0, sizeof(pi), pi, 0, NULL, NULL);

    // Step 10: Finish
    clFinish(queue);

    // Step 11: Print result
    float sum = 0.0f;
    for (int i = 0; i < 1024; i++) {
        sum += pi[i];
    }
    printf("pi = %.20f\n", sum / 1024.0f);

    // Step 12: Clean up
    clReleaseMemObject(pi_buffer);
    clReleaseKernel(kernel);
    clReleaseProgram(program);
    clReleaseCommandQueue(queue);
    clReleaseContext(context);

    return 0;
}

将文件保存为calc_pi.c，然后在命令行中运行以下命令：

gcc -o calc_pi calc_pi.c -lOpenCL
./calc_pi

若输出类似于pi = 3.1415927的结果，则OpenCL已成功安装。

示例二：使用Windows PowerShell运行OpenCL程序

新建一个文本文件，输入以下代码：

#pragma OPENCL EXTENSION cl_khr_fp64 : enable
#pragma OPENCL EXTENSION cl_amd_printf : enable

__kernel void hello(__global double* result)
{
    int gid = get_global_id(0);
    printf("Hello, world! from work item %d\n", gid);
    result[gid] = sin(gid);
}

将文件保存为hello.cl，然后在Windows PowerShell中运行以下命令：

$listPlatform = clinfo.exe | Select-String '^Platform Name:' | Select-Object -Uniq | % { $_.ToString().Replace('Platform Name:', '') }
Write-Host "Available platforms: " $listPlatform
Write-Host "Select a platform: "
$platform = Read-Host
$listDevice = clinfo.exe | Select-String '^Device Name:' | Select-Object -Uniq | % { $_.ToString().Replace('Device Name:', '') }
Write-Host "Available devices: " $listDevice
Write-Host "Select a device"
$device = Read-Host
$cmd = "cl.exe /nologo /O0 /Fe:hello.exe /D_DEBUG /I D:\path\to\OpenCL\include /link /LIBPATH:D:\path\to\OpenCL\lib\x64 /SUBSYSTEM:CONSOLE hello.cl"
Invoke-Expression $cmd
.\hello.exe

若输出类似于以下内容，则OpenCL已成功安装：

Available platforms:  NVIDIA CUDA
Select a platform:
NVIDIA CUDA
Available devices:  GeForce GTX 1080
Select a device
GeForce GTX 1080
Hello, world! from work item 0                              
Hello, world! from work item 1                              
Hello, world! from work item 2                              
Hello, world! from work item 3                              
...