C語言版本的opencl的用法

2021-09-27 03:59:26 字數 3475 閱讀 1383

本文介紹一下c語言使用opencl的基本步驟，系統是windows10，ide是visual studio2017。

step1：你需要安裝一下opencl的windows版本，然後新建乙個工程，在屬性管理器裡面給這個工程匯入opencl的標頭檔案。

step2：匯入標頭檔案

#include #include #include #include #include //我這裡的核函式操作的是影象，所以需要opencv的包


#include #include #include #include #include using namespace cv;


using namespace std;


#pragma warning( disable : 4996 )
step3：獲取平台和上下文

cl_context createcontext()


//建立乙個opencl上下文環境


cl_context_properties contextproperties =


; context = clcreatecontextfromtype(contextproperties, cl_device_type_gpu,


null, null, &errnum);


return context;


}
step4：建立裝置並建立命令佇列

cl_command_queue createcommandqueue(cl_context context, cl_device_id *device)


// 為裝置分配快取空間


devices = new cl_device_id[devicebuffersize / sizeof(cl_device_id)];


errnum = clgetcontextinfo(context, cl_context_devices, devicebuffersize, devices, null);


//char name_data[100];


//clgetdeviceinfo(devices[0], cl_device_name,sizeof(name_data), name_data, null);


//printf("device:%s\n", name_data);


//選取可用裝置中的第乙個


commandqueue = clcreatecommandqueue(context, devices[0], 0, null);


*device = devices[0];


//delete devices;


return commandqueue;


}
step5：構建並且編譯program

cl_program createprogram(cl_context context, cl_device_id device, const char* filename)


std::ostringstream oss;


oss << kernelfile.rdbuf();


std::string srcstdstr = oss.str();


const char *srcstr = srcstdstr.c_str();


program = clcreateprogramwithsource(context, 1,


(const char**)&srcstr,


null, null);


errnum = clbuildprogram(program, 0, null, null, null, null);


return program;


}
step6：建立kernel

// 一、選擇opencl平台並建立乙個上下文


cl_context context = createcontext();


// 二、 建立裝置並建立命令佇列


cl_command_queue commandqueue = createcommandqueue(context, &device);


cl_event histevent = 0;


//建立和構建程式物件


cl_program program = createprogram(context, device, "main.cl");


cl_kernel kernel = clcreatekernel(program, "kernel_rgb2gray", null);
step7：新建檔案main.cl，在裡面新建乙個核函式

__kernel void kernel_rgb2gray(__global unsigned char * rgbimage, 


__global int* result)
step8：為核函式設定引數

mat image = imread("d:");


int imgsize = image.rows * image.cols;


mat srcimage;


cvtcolor(image, srcimage, cv_bgr2gray);


cl_mem memresult = clcreatebuffer(context, cl_mem_write_only,


sizeof(int)*imgsize, null, null);


cl_mem memrgbimage = clcreatebuffer(context, cl_mem_use_host_ptr,


sizeof(uchar) * 3 * imgsize, srcimage.data, null); 


errnum = clsetkernelarg(kernel, 0, sizeof(cl_mem), &memrgbimage);


errnum = clsetkernelarg(kernel, 1, sizeof(cl_mem), &memresult);
step9：執行核函式

int img_h = img.rows;


int img_w = img.cols;


size_t globalthreads[2] = ;


//執行核心函式


errnum = clenqueuendrangekernel(commandqueue, kernel, 2, 0, globalthreads, null,


0, null, &histevent);
step10：獲取執行結果

int result* = new int[imgsize];


errnum = clenqueuereadbuffer(commandqueue, memresult, cl_true, 0,


sizeof(float)*img_h*img_w, result, 1, &histevent, null);

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