in reply to shared array while use ForkManager

Will there be some conflict while I use fork?

You cannot push to an array in the parent with fork; thus any data originating in a child will never be seen by its parent.

In terms of your sample code, our @quality will be a different variable in each child and the parent variable of the same name will never contain data pushed in the children.

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Re^2: shared array while use ForkManager
by mlin (Novice) on Sep 25, 2016 at 09:37 UTC
    OK, Thanks! Is some approach available to solve this prolem?
[reply]

      Many approaches are discussed in perlipc. If you aren't stuck with forks you could also consider threads::shared.

[reply]

      threads or MCE.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
        Thanks!
[reply]

      The MCE::Shared module provides data sharing capabilities. It works reliably with Parallel::ForkManager on Unix platforms. The following is a demonstration via the TIE interface. It is based on the OP's code with slight modification.

      use strict;
use warnings;

use Parallel::ForkManager;
use MCE::Shared;

my $pm = Parallel::ForkManager->new(3);

my @group = (
   [ 'f1','f2','f3' ],
   [ 'f4','f5','f6' ],
   [ 'f7','f8','f9' ]
);

tie my @quality, 'MCE::Shared';

foreach my $i (@group) {
   $pm->start and next;
   foreach my $term (@$i) {
      warn "No such file. - $term\n" and next if ! -e $term;
      ...
      my $IsGood = ...;
      push @quality, $IsGood;
   }
   $pm->finish;
}

$pm->wait_all_children;

print join("\n", @quality), "\n";

      [download]


      The OO interface to MCE::Shared is TIE'less for faster execution.

      use strict;
use warnings;

use Parallel::ForkManager;
use MCE::Shared;

my $pm = Parallel::ForkManager->new(3);

my @group = (
   [ 'f1','f2','f3' ],
   [ 'f4','f5','f6' ],
   [ 'f7','f8','f9' ]
);

my $quality = MCE::Shared->array;

foreach my $i (@group) {
   $pm->start and next;
   foreach my $term (@$i) {
      warn "No such file. - $term\n" and next if ! -e $term;
      ...
      my $IsGood = ...;
      $quality->push($IsGood);
   }
   $pm->finish;
}

$pm->wait_all_children;

print join("\n", $quality->vals), "\n";

      [download]


      Finally, the same thing using MCE::Loop. Due to the nested structure of the array, @group must be back-slashed when passing into mce_loop.

      use strict;
use warnings;

use MCE::Loop max_workers => 3, chunk_size => 1;
use MCE::Shared;

my @group = (
   [ 'f1','f2','f3' ],
   [ 'f4','f5','f6' ],
   [ 'f7','f8','f9' ]
);

my $quality = MCE::Shared->array;

mce_loop {
   my $i = $_;
   foreach my $term (@$i) {
      warn "No such file. - $term\n" and next if ! -e $term;
      ...
      my $IsGood = ...;
      $quality->push($IsGood);
   }
} \@group;

print join("\n", $quality->vals), "\n";

      [download]


      Warm regards, Mario.

[reply]
[d/l]
[select]
        Wow, cool! Thanks a lot!
[reply]

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