Rand Stats




It's fairly straightforward to wire up concurrent progress reporting in Perl 6: just create a Supplier, use it to emit progress reports, and have things wishing to receive progress reports tap the Supply. That's exactly what this module does on this inside; it just saves some boilerplate and helps get a little more intent into the code. It is best suited to cases where "N out of M"-style progress reports are desired, where N reaching M indicates completion. However, it may be used in cases where there is no target also.


In the operation that should report progress, take Concurrent::Progress as a parameter (usually optional) and use it. If no instance is passed, then the method calls will be made on the type object, and will silently do nothing.

sub some-async-operation(Concurrent::Progress :$progress) {
    start {
        # Optionally set a target (get percentage completion calculation
        # for free).
        my @things-to-do = ...;

        # Can add 1 to the count of things completed.
        for @things-to-do {

        # Or can add many.
        for @things-to-do.batch(5) -> @batch {

        # Or can just set the value, if we're counting by ourselves.
        for @things-to-do.kv -> $idx, $obj {
            $progress.set-value($idx + 1);

Meanwhile, in the caller (note that whenever automatically calls Supply on the Concurrent::Progress object):

my $progress = Concurrent::Progress.new;
react {
    whenever $progress -> $status {
        say "$status.value() / $status.target() ($status.percent()%)";

    whenever some-async-operation(:$progress) {
        say "Completed";


A Concurrent::Progress instance will usually be constructed by the initiator of an asynchronous operation. No options are required, but the following may be provided:

Methods for reporting progress

The following methods may be called to report progress:

Methods for receiving progress reports

Progress reports are delivered using a Supply. This is a live Supply, so if it matters that you receive every progress report then be sure to tap it prior to starting the work.

The Supply method is used to obtain the Supply of progress reports (which means a Concurrent::Progress object may be used directly with whenever). The Supply will emit instances of Concurrent::Progress::Report, which has the following properties:

Provided auto-done was not disabled at construction time, then a done will be sent when value reaches target.

It is also possible to pass auto-done and min-interval to the Supply method, in order to override them on a per-Supply basis. This may be useful if you did not have control over the creation of the Concurrent::Progress instance.