[Swift-user] iterate adding dependencies

[Max Hutchinson]

Hello,

I'm using an iterate loop like this:

  progress[0] = 0.;
  step = 5;
  iterate i {
    // Build executable
    if (i == 0){
      // Run from initial condition
      output[i] = run_new();
    } else {
      // Resume from old run
      output[i] = run_old(output[i-1]);
    }
    // Expensive post-processing
    refined[i] = post_process(output[i]);
    progress[i+1] = progress[i] + step;
  } until (progress[i] < 100.);

run_old doesn't depend on refined, but will not run until the post_process
application completes (which is a while; it is expensive).  I'm inferring
that iterate is sequential at the iteration-granularity.

Is this intentional?  I think that iterate is the natural way to express
this computation, but the serialization of run_old wrt post_process is very
expensive.  Is there a case where the assumption that iterations are
evaluated sequentially changes the result of the program?

Max
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