Lionel Rossi

Thanks for your help! I understood what did you told to me

Maybe at the moment i'm looking only for write the correct methods that works without think about the correct way in which i need to write software but i've got exam in these days on Java and i must clear all doubt if i want pass. Then next week i ll start to write good code for the final test (I ll create a programm with all UML diagram).

Best Regards

Well, thanks for your answers but i think that i need some more example to understand well this concept

Stephan van Hulst wrote:Okay, so before you start working with threads, why don't you start by creating a Matrix class that models a single matrix, which contains a multiply(Matrix other) method that returns a new Matrix. You should also add a method determinant() that returns an int.

Try getting this code to work (hint, use unit tests!) and then show us your code, or show us where you get stranded with an explanation of the problem. Don't worry about threads yet!

I just finish the code of Matrix product

import java.util.Scanner; class MatrixProduct extends Thread { private int[][] A; private int[][] B; private int[][] C; private int rig,col; private int dim; public MatrixProduct(int[][] A,int[][] B,int[][] C,int rig, int col,int dim_com) { this.A=A; this.B=B; this.C=C; this.rig=rig; this.col=col; this.dim=dim_com; } public void run() { for(int i=0;i<dim;i++){ C[rig][col]+=A[rig][i]*B[i][col]; } System.out.println("Thread "+rig+","+col+" complete."); } } public class MatrixMultiplication { public static void main(String[] args) { Scanner In=new Scanner(System.in); System.out.print("Row of Matrix A: "); int rA=In.nextInt(); System.out.print("Column of Matrix A: "); int cA=In.nextInt(); System.out.print("Row of Matrix B: "); int rB=In.nextInt(); System.out.print("Column of Matrix B: "); int cB=In.nextInt(); System.out.println(); if(cA!=rB) { System.out.println("We can't do the matrix product!"); System.exit(-1); } System.out.println("The matrix result from product will be "+rA+" x "+cB); System.out.println(); int[][] A=new int[rA][cA]; int[][] B=new int[rB][cB]; int[][] C=new int[rA][cB]; MatrixProduct[][] thrd= new MatrixProduct[rA][cB]; System.out.println("Insert A:"); System.out.println(); for(int i=0;i<rA;i++) { for(int j=0;j<cA;j++) { System.out.print(i+","+j+" = "); A[i][j]=In.nextInt(); } } System.out.println(); System.out.println("Insert B:"); System.out.println(); for(int i=0;i<rB;i++) { for(int j=0;j<cB;j++) { System.out.print(i+","+j+" = "); B[i][j]=In.nextInt(); } } System.out.println(); for(int i=0;i<rA;i++) { for(int j=0;j<cB;j++) { thrd[i][j]=new MatrixProduct(A,B,C,i,j,cA); thrd[i][j].start(); } } for(int i=0;i<rA;i++) { for(int j=0;j<cB;j++) { try{ thrd[i][j].join(); } catch(InterruptedException e){} } } System.out.println(); System.out.println("Result"); System.out.println(); for(int i=0;i<rA;i++) { for(int j=0;j<cB;j++) { System.out.print(C[i][j]+" "); } System.out.println(); } } }

I don't have no idea to how implement the method of determinant

Hi,

I'm newest of the Java programming, i don't use so much the word "static" in variable or methods because i didn't understand well how really do. Can anyone explain me in which situation i can use "static" or better when it recomand to use it?

I already do confusion with another word "final". Which are the difference between this two word?

Best Regards

Campbell Ritchie wrote:Welcome to the Ranch (again)

Why do you say you need several threads?
What is the algorithm for calculating a matrix determinant?

Hi Campbell,

1) For the first point (Product of Matrix) it is the exercise that impose me to use n thread one for each cells i know that is not a good solution but i must do it
2) For calculate the matrix determinant i think that first i need to check the dimension of the matrix (If is 2x2 is simply). For matrix that have a dimension bigger than 2x2 i need to calculate minor complementary so for each step i need to eliminate one row and one column

Stephan van Hulst wrote:Can you explain to us what the problem is that you're experiencing? We can't help you if we don't know what's wrong.

I've got two different problems:

1) I need to create a software for calculate the product of two matrix in which i need to use n thread one for each cells of the matrix result (For this problem i posted a code that calculate the product of matrix but not using n thread for each cells of the matrix result)
2) I need to create a software for calculate the determinant of the matrix using thread (I don't have any idea to how to create a software that do this)

Hi,

I've got a big problem for calculate matrix determinant using thread, is anyone have a code that can pass me for see in which way i can use thread for resolve this problem?

Best Regards

Hi,

I kindly ask you this simply question, in Java every class inherits directly or not directly for the object class. I think because in Java everything is an object and for give to the programmer some guide line for the classes that ll be create and also give some important methods that can be used by other classes (for example toString ecc...). There are other reason and other advantage about this thing?

Best Regards

Hello to everyone,

I know that can be a stupid question, but i kindly ask you if you have a code for matrix multiplication with thread. My problem is that i need to generate n thread one for each cells of the matrix result.

This is the function that i had produce, it works but it doesn't do what i need

import java.util.Random; public class MatrixTest { //Creating the matrix static int[][] mat = new int[3][3]; static int[][] mat2 = new int[3][3]; static int[][] result = new int[3][3]; public static void main(String [] args){ //Creating the object of random class Random rand = new Random(); //Filling first matrix with random values for (int i = 0; i < mat.length; i++) { for (int j = 0; j < mat[i].length; j++) { mat[i][j]=rand.nextInt(10); } } //Filling second matrix with random values for (int i = 0; i < mat2.length; i++) { for (int j = 0; j < mat2[i].length; j++) { mat2[i][j]=rand.nextInt(10); } } try{ //Object of multiply Class Multiply multiply = new Multiply(3,3); //Threads MatrixMultiplier thread1 = new MatrixMultiplier(multiply); MatrixMultiplier thread2 = new MatrixMultiplier(multiply); MatrixMultiplier thread3 = new MatrixMultiplier(multiply); //Implementing threads Thread th1 = new Thread(thread1); Thread th2 = new Thread(thread2); Thread th3 = new Thread(thread3); //Starting threads th1.start(); th2.start(); th3.start(); th1.join(); th2.join(); th3.join(); }catch (Exception e) { e.printStackTrace(); } //Printing the result System.out.println("\n\nResult:"); for (int i = 0; i < result.length; i++) { for (int j = 0; j < result[i].length; j++) { System.out.print(result[i][j]+" "); } System.out.println(); } }//End main }//End Class //Multiply Class class Multiply extends MatrixTest { private int i; private int j; private int chance; public Multiply(int i, int j){ this.i=i; this.j=j; chance=0; } //Matrix Multiplication Function public synchronized void multiplyMatrix(){ int sum=0; int a=0; for(a=0;a<i;a++){ sum=0; for(int b=0;b<j;b++){ sum=sum+mat[chance][b]*mat2[b][a]; } result[chance][a]=sum; } if(chance>=i) return; chance++; } }//End multiply class //Thread Class class MatrixMultiplier implements Runnable { private final Multiply mul; public MatrixMultiplier(Multiply mul){ this.mul=mul; } @Override public void run() { mul.multiplyMatrix(); } }

Anyone can help me please? I know that probably i ll have less fast of the program, but it is an exercise.

Thanks a lot for your cooperation and looking forward into your answer

best Regards