Pushing data into an array in fork

[user2base]

Does someone know how to push data into an array as part of a fork process ??
I always get an empty array.
My code looks like this (I am using Parallel::ForkManager):

my $pid;
my $pm = new Parallel:ForkManager(5);

foreach my $element (@list){
$pid = $pm->start and next;
...
$result = ....
...
push @array, $result;
$pm->finish;
}

print for @array;

 

[usige]

Since you are using fork, the data cannot be shared between processes in a regular array. What you need is something like IPC::Sharable. You'd use it something like:
[tt]
use IPC::Shareable;

# Created array in shared memmory
my %opts = (
create => 1,
mode => 0600,
destroy => 1
);
my $key = 'mkey';

tie @shared_array, 'IPC::Shareable', $key, { %opts } or die "Failed to tie \@shared_array\n";

my $pid;
my $pm = new Parallel:ForkManager(5);

foreach my $element (@list){
$pid = $pm->start and next;
...
$result = ....
...

(tied @shared_array)->shlock; # lock array for update
push @shared_array, $result;
(tied @shared_array)->shunlock; # unlock the array

$pm->finish;
}

$pm->wait_all_children;


print for @shared_array;
[/tt]

The using locks is important so seperate procs don't overwrite each others results. Also don't forget to wait_all_children. If the main proc dies before the children then the shared array will be yanked out form under the children causing errors.

Hope that helps.

 

[MikeLacey]

if you're using Perl 5.8.0 there's a good sharing mechanism for sharing between forked "processes" - on Win32 anyway

Mike

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