Question

Write a C++ program that accepts one command line argument which is an integer n between 2 and 4 inclusive. Generate 60 random integers between 1 and 49 inclusive and store them in a 5 by 12 two dimensional integer array (e.g.,int a[5][12];). Use pthread to create n threads to square all 60 array elements. You should divide this update task among the n threads as evenly as possible. Print the array both before and after the update separately as 5 by 12 matrices. Note: if you do not use pthread to divide the update task among the threads, you may get zero points

Answer 1

#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define COLS 12
#define ROWS 5

int chunkSize;
int n=0;
int arr[ROWS][COLS] ;
void *DoSquare(void *threadid) {
long tid;
  
tid = (long)threadid;
  
int start = tid * chunkSize;
int end=start+chunkSize-1;

  

for(int i=0; i<ROWS; i++){

for(int j=0;j<COLS;j++){

int position = i*COLS + j;

if(position>=start&&position<=end)
{
arr[i][j]=arr[i][j]*arr[i][j];
}
}

}

  
  
  
pthread_exit(NULL);
}

int main () {

cin>>n;
pthread_t threads[n];
int rc;
int i,j,k;


//fill array wil data
for(i=0;i<ROWS;i++)
{
for(j=0;j<COLS;j++)
{
arr[i][j]=(rand() % 49) + 1;
}
}


//Printing Random Array
for(i=0;i<ROWS;i++)
{
cout<<"\n";
for(j=0;j<COLS;j++)
{
cout<<arr[i][j]<<"\t";
}
}

chunkSize = (60 + n - 1) / n; // divide by threads rounded up.

  

for( i = 0; i < n; i++ ) {
cout << "\nmain() : creating thread, " << i << endl;
rc = pthread_create(&threads[i], NULL, DoSquare, (void *)i);
  
if (rc) {
cout << "Error:unable to create thread," << rc << endl;
exit(-1);
}
}
//Printing Resulter Array
for(i=0;i<ROWS;i++)
{
cout<<"\n";
for(j=0;j<COLS;j++)
{
cout<<arr[i][j]<<"\t";
}
}
pthread_exit(NULL);
}