// ----------------------------------------------------------------------------
//
// Matrix multiplication (multi-threaded version).
// (c) Wolfgang Schreiner, 2005.
//
// ----------------------------------------------------------------------------
class MatMultThreads
{
  // matrix dimension
  final static int N = 1024; 

  // number of threads
  static int T;
 
  // shared data used by threads
  static float[][] A0;
  static float[][] B0;
  static float[][] C0;

  static class MultThread extends Thread
  {
    int begin; // index of first row
    int end;   // index of last row + 1

    // -------------------------------------------------------------------------
    // 
    // Create thread in charge of filling C[begin..end-1]
    //
    // -------------------------------------------------------------------------
    public MultThread(int begin, int end)
    {
      this.begin = begin;
      this.end = end;
    }

    // ----------------------------------------------------------------------------
    // 
    // multiply A by B giving C
    // 
    // ----------------------------------------------------------------------------
    public void run()
    {
      for (int i = begin; i < end; i++) 
      {
        for (int j = 0; j < N; j++) 
        {
	  float m = 0;
	  for (int k = 0; k < N; k++) 
	    m = m + A0[i][k]*B0[k][j];
	  C0[i][j] = m;
        }
      }
    }
  }

  // ----------------------------------------------------------------------------
  // 
  // multiply A by B giving C
  // 
  // ----------------------------------------------------------------------------
  static void multiply(float[][] A, float[][] B, float[][] C) 
  {
    A0 = A;
    B0 = B;
    C0 = C;

    int n = N/T;
    MultThread[] thread = new MultThread[T];

    for (int i = 0; i < T; i++) 
    {
      if (i+1 < T)
	thread[i] = new MultThread(i*n, i*n+n);
      else
	thread[i] = new MultThread(i*n, N);
      thread[i].start();
    }

    try
    {
      for (int i = 0; i < T; i++) 
        thread[i].join();
    }
    catch(InterruptedException e) 
    { }
  }

  // ----------------------------------------------------------------------------
  //
  // main program
  //
  // ----------------------------------------------------------------------------
  public static void main(String[] args) 
  {
    if (args.length != 1)
    {
      System.out.println("Usage: MatMultThreads <number of threads>");
      return;
    }
    try
    {
      T = Integer.parseInt(args[0]);
    }
    catch(NumberFormatException e)
    {
      System.out.println("Invalid argument (number expected): " + args[0]);
      return;
    } 

    float[][] A = new float[N][N];
    float[][] B = new float[N][N];
    float[][] C = new float[N][N];
    multiply(A, B, C);
  }
}