[ExM Users] Implicit blocking on foreach construct?

[Tim Armstrong]

Hi Tim,
  It's possible if you reformulate the problem in terms of data flow-
there's no direct way in Swift to ask "is the loop finished" - but there is
a way to ask "is the data being computed by the loop finished".

The "wait" construct - it lets you execute a block of code after a bit of
data is assigned.

E.g. a trivial example is

int x = do_some_computation();
wait (x) {
  trace("x is done!");
}

If you're building an array of files or similar, it's a little more
complicated:

import io;
import files;

file x[];

wait deep (x) {
  trace("Done");
}

foreach i in [1:10] {
  file tmp<"/tmp/swift-tmp-" + i + ".txt">;

  tmp = write("");

  x[i] = tmp;
}

This only prints "Done" once all of the files have been written.  The wait
deep ensures that everything in the array is completely built.

I'm also not sure about your use case, but Swift has some built-in support
for generating temporary files - Justin Wozniak was recently working on
improving that.

- Tim

On 17 March 2015 at 15:08, Timothy Stitt (TGAC) <Timothy.Stitt at tgac.ac.uk>
wrote:

>  Hi all,
>
>  Is there a way to add explicit blocking to the end of the foreach
> construct? I have the following logic which doesn't work right now as the
> delete_files() routine is assumed to be concurrent with the foreach block
> when I want it to execute after the foreach block is completed for all
> workers:
>
>  foreach { do some work creating temp files}
> delete_files() // delete temp files using an app function
>
>  Thanks,
>
>  Tim.
>
> ---
>
> *Timothy Stitt PhD* / Head of Scientific Computing
>
> The Genome Analysis Centre (TGAC)
>
> http://www.tgac.ac.uk/
>
>
>  p: +44 1603 450378
>
> e: timothy.stitt at tgac.ac.uk
>
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