OpenCL入门

初入OpenCL,做个记录。

在Windows下开发OpenCL程序，必须先下载OpenCL的SDK，现在AMD，NVIDIA，Intel均提供各自的OpenCL库，基本是大同小异。安装好SDK后新建Win32控制台项目，然后需要配置下包含文件路径和库路径，具体见下图（我安装的Intel的SDK ）。

1.其中那个包含Intel的路径就是包含cl.h文件的目录。

2.如图中那个Intel的lib目录

3.添加需要连接的静态库OpenCL.lib

配置完成后就可以开始写代码调试了，OpenCL的初始化还是很复杂的，和CUDA几行代码搞定完全没可比性，刚开始可能对流程不太熟悉，慢慢熟悉就好，当然也可以自己写个框架来做这些复杂的初始化工作。OpenCL的内核代码是即时编译的，代码中我为了方便没有从cl文件中读入Kernel代码，直接以字符串的形式定义了。

 #include "stdafx.h"

 #include <iostream>
 #include <fstream>
 #include <string.h>
 #include <vector>
 using namespace std;

 #if defined(__APPLE__) || defined(__MACOSX)
 #include <OpenCL/cl.hpp>
 #else
 #include <CL/cl.h>
 #endif

 #define KERNEL(...) #__VA_ARGS__

 #define ARRAY_X_LEN 16
 #define ARRAY_Y_LEN 16

 const char *kernelSourceCode = KERNEL(
     __kernel void VecAdd(__global int *buffer1, __global int *buffer2, __global int *buffer3)
 {
         size_t idx = get_global_id();
         size_t idy = get_global_id();
         int dimX = get_global_size();
         int dimY = get_global_size();
         int id = idx + idy*dimX;
         buffer3[id] = buffer1[id] + buffer2[id];
     });

 int main()
 {
     cl_int status = ;
     size_t deviceListSize;
     cl_uint numPlatforms;
     cl_platform_id platform = NULL;
     status = clGetPlatformIDs(, NULL, &numPlatforms);
     if (status != CL_SUCCESS)
     {
         printf("获取平台数目失败");
         return EXIT_FAILURE;
     }
     if (numPlatforms >)
     {
         cl_platform_id* platforms = (cl_platform_id*)malloc(numPlatforms*sizeof(cl_platform_id));
         status = clGetPlatformIDs(numPlatforms, platforms, NULL);
         if (status != CL_SUCCESS)
         {
             printf("初始化平台失败");
             return -;
         }
         for (unsigned int i = ; i<numPlatforms; ++i)
         {
             char *vendor = (char*)malloc();
             status = clGetPlatformInfo(platforms[i], CL_PLATFORM_VENDOR, sizeof(vendor), vendor, NULL);
             platform = platforms[i];
             if (!strcmp(vendor, "NVIDIA Corporation"))
             {
                 break;
             }
         }
         delete platforms;
     }
     cl_context_properties cps[] = { CL_CONTEXT_PLATFORM, (cl_context_properties)platform,  };
     cl_context_properties* cprops = (NULL == platform) ? NULL : cps;
     cl_context context = clCreateContextFromType(cprops, CL_DEVICE_TYPE_GPU, NULL, NULL, &status);
     if (status != CL_SUCCESS)
     {
         printf("创建上下文失败");
         return EXIT_FAILURE;
     }
     status = clGetContextInfo(context, CL_CONTEXT_DEVICES, , NULL, &deviceListSize);
     if (status != CL_SUCCESS)
     {
         printf("获取设备数目失败");
         return EXIT_FAILURE;
     }
     cl_device_id *devices = (cl_device_id *)malloc(deviceListSize);
     if (devices == )
     {
         printf("为设备分配空间失败");
         return EXIT_FAILURE;
     }
     status = clGetContextInfo(context, CL_CONTEXT_DEVICES, deviceListSize, devices, NULL);
     if (status != CL_SUCCESS)
     {
         printf("初始化设备失败");
         return EXIT_FAILURE;
     }

     size_t sourceSize[] = { strlen(kernelSourceCode) };
     cl_program program = clCreateProgramWithSource(context, , &kernelSourceCode, sourceSize, &status);
     if (status != CL_SUCCESS)
     {
         printf("创建程序失败");
         return EXIT_FAILURE;
     }
     status = clBuildProgram(program, , devices, NULL, NULL, NULL);
     if (status != CL_SUCCESS)
     {
         printf("编译程序失败");
         return EXIT_FAILURE;
     }
     cl_kernel kernel = clCreateKernel(program, "VecAdd", &status);
     if (status != CL_SUCCESS)
     {
         printf("创建内核失败");
         return EXIT_FAILURE;
     }
     cl_command_queue commandQueue = clCreateCommandQueue(context, devices[], , &status);
     if (status != CL_SUCCESS)
     {
         printf("创建命令队列失败");
         return EXIT_FAILURE;
     }
     int arrayLenght = ARRAY_X_LEN*ARRAY_Y_LEN;
     int arraySize = arrayLenght*sizeof(int);

     int *hA = new int[arrayLenght];
     int *hB = new int[arrayLenght];
     int *hC = new int[arrayLenght];

     memset(hA, , arraySize);
     memset(hB, , arraySize);
     memset(hC, , arraySize);

     for (int i = ; i<arrayLenght; i++)
     {
         hA[i] = i;
         hB[i] = i;
     }

     cl_mem dA = clCreateBuffer(context, CL_MEM_ALLOC_HOST_PTR, arraySize, NULL, &status);
     if (status != CL_SUCCESS)
     {
         printf("创建内存对象失败");
         return EXIT_FAILURE;
     }
     cl_mem dB = clCreateBuffer(context, CL_MEM_ALLOC_HOST_PTR, arraySize, NULL, &status);
     if (status != CL_SUCCESS)
     {
         printf("创建内存对象失败");
         return EXIT_FAILURE;
     }
     cl_mem dC = clCreateBuffer(context, CL_MEM_ALLOC_HOST_PTR, arraySize, NULL, &status);
     if (status != CL_SUCCESS)
     {
         printf("创建内存对象失败");
         return EXIT_FAILURE;
     }
     status = clEnqueueWriteBuffer(commandQueue, dA, CL_TRUE, , arraySize, hA, , NULL, NULL);
     if (status != CL_SUCCESS)
     {
         printf("输入值写入内存对象失败");
         return EXIT_FAILURE;
     }
     status = clEnqueueWriteBuffer(commandQueue, dB, CL_TRUE, , arraySize, hB, , NULL, NULL);
     if (status != CL_SUCCESS)
     {
         printf("输入值写入内存对象失败");
         return EXIT_FAILURE;
     }
     status = clSetKernelArg(kernel, , sizeof(cl_mem), (void*)&dA);
     if (status != CL_SUCCESS)
     {
         printf("设置内核参数失败");
         return EXIT_FAILURE;
     }
     status = clSetKernelArg(kernel, , sizeof(cl_mem), (void*)&dB);
     if (status != CL_SUCCESS)
     {
         printf("设置内核参数失败");
         return EXIT_FAILURE;
     }
     status = clSetKernelArg(kernel, , sizeof(cl_mem), (void*)&dC);
     if (status != CL_SUCCESS)
     {
         printf("设置内核参数失败");
         return EXIT_FAILURE;
     }
     size_t globalThreads[] = { ARRAY_X_LEN, ARRAY_Y_LEN };
     size_t localThreads[] = { ,  };
     status = clEnqueueNDRangeKernel(commandQueue, kernel, , NULL, globalThreads, localThreads, , NULL, NULL);
     if (status != CL_SUCCESS)
     {
         printf("将内核放入命令队列失败");
         return EXIT_FAILURE;
     }
     status = clFinish(commandQueue);
     if (status != CL_SUCCESS)
     {
         printf("队列还没有完成");
         return EXIT_FAILURE;
     }
     status = clEnqueueReadBuffer(commandQueue, dC, CL_TRUE, , arraySize, hC, , NULL, NULL);
     if (status != CL_SUCCESS)
     {
         printf("读内存对象失败");
         return EXIT_FAILURE;
     }
     printf("结果:\n");
     for (int i = ; i<arrayLenght; i++)
     {
         printf("%d ", hC[i]);
         if ((i + ) % ARRAY_X_LEN == )
             printf("\n");
     }
     status = clReleaseKernel(kernel);
     status = clReleaseProgram(program);
     status = clReleaseMemObject(dA);
     status = clReleaseMemObject(dB);
     status = clReleaseMemObject(dC);
     status = clReleaseCommandQueue(commandQueue);
     status = clReleaseContext(context);
     free(devices);
     delete [] hA;
     delete [] hB;
     delete [] hC;
     return ;
 }

运行结果：