Programming examples

In this section we only give out example programs to show the new language features.

The first example is Choleski decomposition,

Procs1 p = new Procs1(4);
on(p) {
  Range x = new CyclicRange(n, p.dim(0));
  float a[[*,]] = new float [[n, x]];

  float b[[*]] = new float [[n]];
                      // buffer

  ... some code to initialise `a' ...

  for(int k = 0 ; k < N - 1 ; k++) {
    at(l = x[k]) {
      float d =  Math.sqrt(a[k,l]) ;
      a[k,l] = d ;
      for(int s = k + 1 ; s < N ; s++)
        a[s,l] /= d ;
    }

    Adlib.remap(b[[k+1:]], a[[k+1:,  k]]);

    overall(m = x | k + 1 : )
      for(int i = x.idx(m) ; i < N ; i++)
        a[i,m] -= b[i] * b[x.idx(m)] ;
  }

  at(l = x [N - 1])
    a[N - 1,l] = Math.sqrt(a[N-1,l]) ;
}

Here, remap is used to broadcast one updated column to each process.

The second example is Jacobi iteration,

Procs2 p = new Procs2(2, 4);
Range
    x = new BlockRange(100, p.dim(0), 1),
    y = new BlockRange(200, p.dim(1), 1); 
on(p) {
  float [[,]] a = new int [[x,y]] ;
  ... some code to initialize `a'

  float [[,]] b = new int [[x,y]];

  Adlib.writeHalo(a);

  overall(i=x|:)
    overall(j=y|:)
      b[i,j] = 0.25 * (a[i-1,j] + 
          a[i+1,j] + a[i,j-1] + a[i,j+1]);
  overall(i=x|:)
    overall(j=y|:)
      a[i,j] = b[i,j];
}

In the above code, there is only one iteration, it is used to demonstrate how to define range reference with halo area, and how to use the writeHalo function.