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Matrix Multiplication (Square of a Matrix) using Threads in JAVA

April 28, 2019
This program will take a text file as a command line argument. The text file will have the first row indicating the total number of rows and columns which will be equal as this program is programmed to read a square matrix from a file and calculate its square using threads.

 Content of the text file to be given as an argument

 14
0 1 0 7 5 3 1 0 1 0 7 5 3 1
2 0 0 3 2 2 2 3 0 2 9 0 2 3
2 1 1 2 2 2 4 0 0 2 4 3 3 5
3 0 2 9 0 2 6 1 2 3 4 5 6 7
2 0 0 3 2 2 2 3 0 2 9 0 2 3
2 1 1 2 2 2 4 0 0 2 4 3 3 5
3 0 2 9 0 2 6 1 2 3 4 5 6 7
0 1 0 7 5 3 1 2 0 0 3 2 2 2
3 0 2 9 0 2 3 2 1 1 2 2 2 4
0 0 2 4 3 3 5 3 0 2 9 0 2 6
1 2 3 4 5 6 7 0 1 0 7 5 3 1
2 0 0 3 2 2 2 3 0 2 9 0 2 3
2 1 1 2 2 2 4 0 0 2 4 3 3 5
3 0 2 9 0 2 6 1 2 3 4 5 6 7

 The first row indicates the total number of rows and columns, in this case, rows=cloumns=14.
And the next rows will be the actual matrix which we want to multiply with itself. The program will calculate the square of the matrix written in your file.

 
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import java.util.*;

import java.io.*; 

class MMThread extends Thread{  

  int row=0,k,j,sum=0;

 int first[][],multiply[][];

  MMThread(int row,int first[][],int multiply[][]){

  this.row = row;

  this.first = first;

  this.multiply = multiply;

 } 

 public void run(){  

  for (j = 0; j < first[row].length; j++){

           for (k = 0; k < first.length; k++){

              sum = sum + first[row][k]*first[k][j];

           }

           multiply[row][j] = sum;

           sum = 0;

        }

 } 

}

public class MM{

   public static void main(String args[])  throws IOException

   {

   int rows=0,cols=0,i=0,j=0,line=0;

    if(args.length==0){

    System.out.println("Matrix File Not Provided");

    return;

   }

    Scanner scanner = new Scanner(new File(args[0]));

    int first[][] = null;

    while(scanner.hasNextInt())

  {

   if(line==0){

    rows = scanner.nextInt();

    cols = rows;

    first = new int [rows][cols];

    line++;

   }

      first[i][j] = scanner.nextInt();

      if(j==rows-1){

       i++;

       j=0;

      }else{

       j++;

      }

  }

    System.out.println("\nOriginal Matrix\n");

    for (i = 0; i < rows; i++){

      for (j = 0; j < cols; j++)

         System.out.print(first[i][j]+"\t");

     System.out.println();

   }

     int second[][] = first;

     int multiply[][] = new int[rows][cols];

     MMThread mMThread[] = new MMThread[rows];

     for(int l=0;l<mMThread.length;l++){

      mMThread[l] = new MMThread(l,first,multiply);

      mMThread[l].start();

     }

     while(Thread.activeCount() > 1);

     System.out.println("\nProduct of the matrices:\n");

     for (i = 0; i < rows; i++){

        for (j = 0; j < cols; j++)

           System.out.print(multiply[i][j]+"\t");

        System.out.print("\n");

     }

   }

}

Output:

square of a matrix using threads in java

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