我正在使用notebook上的opencv242 + VS2010。
我尝试测试OpenCV中的GPU块，但结果显示GPU运行比CPU代码慢100倍。
在这段代码中，我只是将彩色图像转换为灰度图像，使用了cvtColor函数。
这是我的代码，PART1是CPU代码（测试CPU RGB2GRAY），PART2是上传图像到GPU，PART3是GPU RGB2GRAY，PART4是再次使用CPU RGB2GRAY。 有三件事让我非常惊讶：
1 在我的代码中，part1只需0.3毫秒，而与part1完全相同的part4需要40毫秒！！！
2 上传图像到GPU的part2需要6000毫秒！！！
3 Part3（GPU代码）需要11毫秒，对于这个简单的图像来说太慢了！
#include "StdAfx.h"
#include <iostream>
#include "opencv2/opencv.hpp"
#include "opencv2/gpu/gpu.hpp"
#include "opencv2/gpu/gpumat.hpp"
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <cuda.h>
#include <cuda_runtime_api.h>
#include <ctime>
#include <windows.h>
using namespace std;
using namespace cv;
using namespace cv::gpu;
int main()
{
LARGE_INTEGER freq;
LONGLONG QPart1,QPart6;
double dfMinus, dfFreq, dfTim;
QueryPerformanceFrequency(&freq);
dfFreq = (double)freq.QuadPart;
cout<<getCudaEnabledDeviceCount()<<endl;
Mat img_src = imread("d:\\CUDA\\train.png", 1);
// PART1 CPU code~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// From color image to grayscale image.
QueryPerformanceCounter(&freq);
QPart1 = freq.QuadPart;
Mat img_gray;
cvtColor(img_src,img_gray,CV_BGR2GRAY);
QueryPerformanceCounter(&freq);
QPart6 = freq.QuadPart;
dfMinus = (double)(QPart6 - QPart1);
dfTim = 1000 * dfMinus / dfFreq;
printf("CPU RGB2GRAY running time is %.2f ms\n\n",dfTim);
// PART2 GPU upload image~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GpuMat gimg_src;
QueryPerformanceCounter(&freq);
QPart1 = freq.QuadPart;
gimg_src.upload(img_src);
QueryPerformanceCounter(&freq);
QPart6 = freq.QuadPart;
dfMinus = (double)(QPart6 - QPart1);
dfTim = 1000 * dfMinus / dfFreq;
printf("Read image running time is %.2f ms\n\n",dfTim);
GpuMat dst1;
QueryPerformanceCounter(&freq);
QPart1 = freq.QuadPart;
/*dst.upload(src_host);*/
dst1.upload(imread("d:\\CUDA\\train.png", 1));
QueryPerformanceCounter(&freq);
QPart6 = freq.QuadPart;
dfMinus = (double)(QPart6 - QPart1);
dfTim = 1000 * dfMinus / dfFreq;
printf("Read image running time 2 is %.2f ms\n\n",dfTim);
// PART3~ GPU code~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// gpuimage From color image to grayscale image.
QueryPerformanceCounter(&freq);
QPart1 = freq.QuadPart;
GpuMat gimg_gray;
gpu::cvtColor(gimg_src,gimg_gray,CV_BGR2GRAY);
QueryPerformanceCounter(&freq);
QPart6 = freq.QuadPart;
dfMinus = (double)(QPart6 - QPart1);
dfTim = 1000 * dfMinus / dfFreq;
printf("GPU RGB2GRAY running time is %.2f ms\n\n",dfTim);
// PART4~CPU code(again)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// gpuimage From color image to grayscale image.
QueryPerformanceCounter(&freq);
QPart1 = freq.QuadPart;
Mat img_gray2;
cvtColor(img_src,img_gray2,CV_BGR2GRAY);
BOOL i_test=QueryPerformanceCounter(&freq);
printf("%d \n",i_test);
QPart6 = freq.QuadPart;
dfMinus = (double)(QPart6 - QPart1);
dfTim = 1000 * dfMinus / dfFreq;
printf("CPU RGB2GRAY running time is %.2f ms\n\n",dfTim);
cvWaitKey();
getchar();
return 0;
}