将oclMat发送到函数会在运行时产生巨大差异(sending oclMat to function creates huge difference in runtime)

 我用3个输入写了一个函数（masking）： 
 
 
 
 inputOCL - 一个oclMat 
 
 
 comparisonValue - 双精度值 
 
 
 method - 确定比较方法的int变量 
 
 
 对于我的例子，我选择了method = 1，它代表CMP_GT，测试inputOCL> comparisonValue是否元素。 
 
 该函数的目的是将inputOCL中不符合给定copma的所有元素清零。 
 
 这是功能屏蔽： 
 
void masking(cv::ocl::oclMat inputOCL, double comparisonValue, int method){
// NOTE: method can be set to 1-->5 corresponding to (==, >, >=, <, <=, !=)

cv::ocl::oclMat valueOCL(inputOCL.size(), inputOCL.type());
valueOCL.setTo(cv::Scalar(comparisonValue));
cv::ocl::oclMat logicalOCL;
cv::ocl::compare(inputOCL, valueOCL, logicalOCL, method);
logicalOCL.convertTo(logicalOCL, inputOCL.type());
cv::ocl::multiply(logicalOCL, inputOCL, inputOCL);  
cv::ocl::multiply(1 / 255.0, inputOCL, inputOCL); }
 
 在对函数进行计时时，我发现运行函数或运行以下代码时直接运行计算时运行时间差异很大： 
 
int main(int argc, char** argv){

double value1 = 1.23456789012345;
double value2 = 1.23456789012344;

// initialize matrix
cv::Mat I(5000, 5000, CV_64F, cv::Scalar(value1));
// copy input to GPU
cv::ocl::oclMat inputOCL(I);
int method = 1;
static double start_TIMER;

// computation done in function
start_TIMER = cv::getTickCount();
masking(inputOCL, value2, method);
std::cout << "\nFunction runtime = " << ((double)(cv::getTickCount() - start_TIMER)) / cv::getTickFrequency() << " Seconds\n";

// direct computation
start_TIMER = cv::getTickCount();
cv::ocl::oclMat valueOCL(inputOCL.size(), inputOCL.type());
valueOCL.setTo(cv::Scalar(value2));
cv::ocl::oclMat logicalOCL;
cv::ocl::compare(inputOCL, valueOCL, logicalOCL, method);
logicalOCL.convertTo(logicalOCL, inputOCL.type());
cv::ocl::multiply(logicalOCL, inputOCL, inputOCL);
cv::ocl::multiply(1 / 255.0, inputOCL, inputOCL);
std::cout << "\nDirect runtime = " << ((double)(cv::getTickCount() - start_TIMER)) / cv::getTickFrequency() << " Seconds\n";
}
 
 运行时可以在此屏幕截图中看到： 
 
 
 为什么运行时有这么大的差异？ 

I wrote a function (masking) with 3 inputs:
 
 
 
inputOCL - an oclMat
 
 
comparisonValue - a double value
 
 
method - an int variable determining the comparison method
 
 
For my example I chose method=1, which stands for CMP_GT, testing if inputOCL>comparisonValue element-wise.
 
The purpose of the function is to zero out all the elements in inputOCL that don't comply with the given copmarison.
 
Here is the function masking:
 
void masking(cv::ocl::oclMat inputOCL, double comparisonValue, int method){
// NOTE: method can be set to 1-->5 corresponding to (==, >, >=, <, <=, !=)

cv::ocl::oclMat valueOCL(inputOCL.size(), inputOCL.type());
valueOCL.setTo(cv::Scalar(comparisonValue));
cv::ocl::oclMat logicalOCL;
cv::ocl::compare(inputOCL, valueOCL, logicalOCL, method);
logicalOCL.convertTo(logicalOCL, inputOCL.type());
cv::ocl::multiply(logicalOCL, inputOCL, inputOCL);  
cv::ocl::multiply(1 / 255.0, inputOCL, inputOCL); }
 
When timing the function I find a very large difference in runtime between running the function or running the computation directly when running the following code:
 
int main(int argc, char** argv){

double value1 = 1.23456789012345;
double value2 = 1.23456789012344;

// initialize matrix
cv::Mat I(5000, 5000, CV_64F, cv::Scalar(value1));
// copy input to GPU
cv::ocl::oclMat inputOCL(I);
int method = 1;
static double start_TIMER;

// computation done in function
start_TIMER = cv::getTickCount();
masking(inputOCL, value2, method);
std::cout << "\nFunction runtime = " << ((double)(cv::getTickCount() - start_TIMER)) / cv::getTickFrequency() << " Seconds\n";

// direct computation
start_TIMER = cv::getTickCount();
cv::ocl::oclMat valueOCL(inputOCL.size(), inputOCL.type());
valueOCL.setTo(cv::Scalar(value2));
cv::ocl::oclMat logicalOCL;
cv::ocl::compare(inputOCL, valueOCL, logicalOCL, method);
logicalOCL.convertTo(logicalOCL, inputOCL.type());
cv::ocl::multiply(logicalOCL, inputOCL, inputOCL);
cv::ocl::multiply(1 / 255.0, inputOCL, inputOCL);
std::cout << "\nDirect runtime = " << ((double)(cv::getTickCount() - start_TIMER)) / cv::getTickFrequency() << " Seconds\n";
}
 
The runtimes can be seen in this screenshot:
 
 
Why is there such a large difference in runtimes?

原文：https://stackoverflow.com/questions/30319096