Addition and Subtraction of Matrix using pthreads in C/C++

Here we will see how to perform the matrix addition and subtraction using multithreaded environment. The pthread is used to execute multiple threads simultaneously in C or C++.

There are two matrices A and B. Order of each matrix is (m x n). Each thread will take each row, and perform addition or subtraction. So for m rows, there are m different threads.

Example

#include<iostream> #include <pthread.h> #include <cstdlib> #include <cstdint> #define CORE 3 #define MAX 3 using namespace std; int AMat[MAX][MAX] = {{10, 20, 30},    {40, 50, 60},    {70, 80, 50} }; int BMat[MAX][MAX] = {{80, 60, 20},    {30, 20, 15},    {10, 14, 35} }; pthread_t thread[CORE * 2]; int add[MAX][MAX], sub[MAX][MAX]; void* addMatrices(void* arg) {    intptr_t core = (intptr_t)arg;    // Each thread computes 1/3rd of matrix addition    for (int i = core * MAX / 3; i < (core + 1) * MAX / 3; i++) {       for (int j = 0; j < MAX; j++) {          add[i][j] = AMat[i][j] + BMat[i][j];       }    } } void* subtraction(void* arg) {    intptr_t core = (intptr_t)arg;    // Each thread computes 1/3rd of matrix subtraction    for (int i = core * MAX / 3; i < (core + 1) * MAX / 3; i++) {       for (int j = 0; j < MAX; j++) {          sub[i][j] = AMat[i][j] - BMat[i][j];       }    } } void display(){    cout << "Matrix A: " << endl;    for(int i = 0; i < MAX; i++) {       for(int j = 0; j < MAX; j++) {          cout << AMat[i][j] << " ";       }       cout << endl;    }    cout << "\nMatrix B: " << endl;    for(int i = 0; i < MAX; i++) {       for(int j = 0; j < MAX; j++) {          cout << BMat[i][j] << " ";       }       cout << endl;    } } void displayRes(){    cout << "\nAddition: " << endl;    for(int i = 0; i < MAX; i++) {       for(int j = 0; j < MAX; j++) {          cout << add[i][j] << " ";       }       cout << endl;    }    cout << "\nSubtraction: " << endl;    for(int i = 0; i < MAX; i++) {       for(int j = 0; j < MAX; j++) {          cout << sub[i][j] << " ";       }       cout << endl;    } } main() {    display();    int step = 0;    for (int i = 0; i < CORE; i++) {       pthread_create(&thread[i], NULL, &addMatrices, (void*)step);       pthread_create(&thread[i + CORE], NULL, &subtraction, (void*)step);       step++;    }    for (int i = 0; i < CORE * 2; i++) {       pthread_join(thread[i], NULL);    }    displayRes(); }

Output

Matrix A: 10 20 30 40 50 60 70 80 50 Matrix B: 80 60 20 30 20 15 10 14 35 Addition: 90 80 50 70 70 75 80 94 85 Subtraction: -70 -40 10 10 30 45 60 66 15