#!/opt/perl/bin/perl

## http://www.perlmonks.org/?node_id=1182580

use strict;
use warnings;

use MCE;
use Time::HiRes 'time';

my $iterations = 100;
my $chunksize = 50;
my $threads = 5;
my $output = "m.txt";

my %data = ();

foreach ('a'..'z') {
   $data{$_} = $_ x 200;
}

test_mce();

sub test_mce {
   my $start = time;

   my $mce = MCE->new(
      max_workers => $threads, chunk_size => $chunksize,
      input_data => make_iter_input($chunksize, $iterations),
      gather => make_iter_output($output),
      user_func => \&work,
   )->run();

   printf STDERR "testa done in %0.02f seconds\n", time - $start;
}

# MCE task to run in parallel

sub work {
   my ($mce, $chunk_ref, $chunk_id) = @_;
   my $data = $chunk_ref->[0];
   my @ret = ();

   foreach my $chunk (@$data) {
      my %output = ();

      foreach my $key (keys %$chunk) {
         if ($key eq '.') {
            $output{$key} = $$chunk{$key};
            next;
         }
         my $val = $$chunk{$key};
         my $uc = uc($key);
         $val =~ s/$key/$uc/g;
         $output{$key} = $val;
      }

      push(@ret,\%output);
   }

   MCE->gather($chunk_id, \@ret);
}

# make an input closure, returns an iterator

sub make_iter_input {
   my ($chunk_size, $iterations) = @_;
   my $seq_a = 1;

   return sub {
      return if $seq_a > $iterations;
      my ($chunk_size) = @_;
      my @chunk = ();

      foreach my $seq_b ( 1 .. $chunk_size ) {
         my %retdata = %data;
         $retdata{'.'} = $seq_a * $seq_b;
         push @chunk, \%retdata;
      }

      $seq_a += 1;
      return \@chunk;
   };
}

# make an output closure, returns an iterator

sub make_iter_output {
   my ($path) = @_;
   my %hold; my $order_id = 1;

   open my $fh, '>', $path or die "open error: $!";

   return sub {
      my $chunk_id = shift;

      # hold temporarily, until orderly
      $hold{$chunk_id} = shift;  # \@ret

      while (1) {
         last unless exists $hold{$order_id};

         foreach my $data (@{ delete $hold{$order_id} }) {
            foreach my $key (sort keys %$data) {
               print {$fh} $$data{$key};
            }
            print {$fh} "\n";
         }

         $order_id++;
      }
   };
}