MP Implementation

Include the Library #include "omp.h"

Read the image

char* imageName = argv[1];
Mat image;
image = imread( imageName, IMREAD_COLOR );
if( !image.data )
{
	printf( " No image data \n " );
	return -1;
}

Read arguments given if available and Initialize Radius kernel and number of threads

if(argv[2]==NULL || argc<3) {
	radius = 3;
	NUM_THREADS = 4;
	std::cout<<"Radius and NUM_THREADS are null"<<std::endl;
}
else {
	radius = atoi(argv[2]);
}

if (argv[3]==NULL || argc<4) {
	NUM_THREADS = 4;
	std::cout<<"NUM_THREADS is null"<<std::endl;
}
else {
	NUM_THREADS = atoi(argv[3]);
}

Declare the offset and take the current time

int protect = radius + 1;
//always radius less than protect, minimun value = 2

//take the time
struct timespec start, finish;
double elapsed;

clock_gettime(CLOCK_MONOTONIC, &start);
double start_omp_time = omp_get_wtime();

Use library methods to set the number of threads and launch it in parallel

omp_set_num_threads(NUM_THREADS);

#pragma omp parallel for
for (int i = protect; i < image.rows - protect; ++i)
{
	for (int j = protect; j < image.cols - protect; ++j)
	{

		//(i+1,j) right
		//(i-1,j) left
		//(i,j+1) down
		//(i,j-1) top

		//RED
		blur.at<Vec3b>(i,j)[0] = (image.at<Vec3b>(i+radius,j)[0] + image.at<Vec3b>(i-radius,j)[0] + image.at<Vec3b>(i,j+radius)[0] + image.at<Vec3b>(i,j-radius)[0])/4;

		//GREEN
		blur.at<Vec3b>(i,j)[1] = (image.at<Vec3b>(i+radius,j)[1] + image.at<Vec3b>(i-radius,j)[1] + image.at<Vec3b>(i,j+radius)[1] + image.at<Vec3b>(i,j-radius)[1])/4;

		//BLUE
		blur.at<Vec3b>(i,j)[2] = (image.at<Vec3b>(i+radius,j)[2] + image.at<Vec3b>(i-radius,j)[2] + image.at<Vec3b>(i,j+radius)[2] + image.at<Vec3b>(i,j-radius)[2])/4;

	}
}

Get the elapsed time and write the output results for future analysis

clock_gettime(CLOCK_MONOTONIC, &finish);
elapsed = (finish.tv_sec - start.tv_sec);
elapsed += (finish.tv_nsec - start.tv_nsec) / 1000000000.0;
std::cout<<"Time: "<< elapsed << std::endl;
std::cout<<"Omp Time: "<< omp_get_wtime() - start_omp_time << std::endl;

//write in file
std::ofstream output;
output.open("mainopenmpResult.txt", std::ofstream::app | std::ofstream::out );
output<< imageName <<", "<< radius << ", " << NUM_THREADS <<", "<< elapsed << std::endl;
output.close();