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(size, p.dim(0));
    float a[[,#]] = new float [[size, x]];
    // initialize the array here;
    float b[[]] = new float [[size]]; // as a buffer

    at(j=x[0])
      a[0,j]=Math.sqrt(a[0,j]);

    for(int k=0; k<size-1; k++) {
      for(int s=k+1; s<size; s++)
        at(j=x[k])
          a[s,j]/=a[j,j];

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

      over (j=x|k+1:)
        for (int i=x; i<size; i++)
          a[i,j]-=b[i]*b[j];

      at(j=x[k+1])
        a[k+1,j]=Math.sqrt(a[k+1,j]);

    }
  }

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); 
  Range 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);

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