in reply to IPC:Shareable: Not an array reference

After writing a solution using MCE::Shared, I wanted to come back and give IPC::Shareable a try including locking. Here it is.

use strict;
use warnings;

use IPC::Shareable;

my ( $glue, $options ) = ( 'data', {
   create    => 1,
   exclusive => 0,
   mode      => 0644,
   destroy   => 1,
});

tie my @data, 'IPC::Shareable', $glue, $options;

if ( ! defined ( my $pid = fork() ) ) {
   die "Cannot fork!: $!";
}
elsif ( $pid == 0 ) {
   # Child
   my $item;
   sleep 1;

   for ( my $i = 1; $i <= 10; $i++ ) {
      ( tied @data )->shlock;
      $item = shift @data;
      ( tied @data )->shunlock;

      $item = '' if ( ! defined $item );
      print "Child: $item\n";
   }
}
else {
   # Parent
   for ( my $i = 1; $i <= 10; $i++ ) {
      ( tied @data )->shlock;
      push @data, $i;
      ( tied @data )->shunlock;

      print "Parent: @data\n";
   }

   waitpid( $pid, 0 );
}

[download]

It produces the following output on FreeBSD, Linux, and Mac OS X.

Parent: 1
Parent: 1 2
Parent: 1 2 3
Parent: 1 2 3 4
Parent: 1 2 3 4 5
Parent: 1 2 3 4 5 6
Parent: 1 2 3 4 5 6 7
Parent: 1 2 3 4 5 6 7 8
Parent: 1 2 3 4 5 6 7 8 9
Parent: 1 2 3 4 5 6 7 8 9 10
Child: 1
Child: 2
Child: 3
Child: 4
Child: 5
Child: 6
Child: 7
Child: 8
Child: 9
Child: 10

[download]

Notice how the construction for the shared variable is done before spawning. Also, the parent waits for the spawned worker to exit. Other than locking (optional for this use-case due to sleep in worker), everything else is similar to the OP's code.

Regards, Mario.

Replies are listed 'Best First'.
Re^2: IPC:Shareable: Not an array reference
by marioroy (Prior) on Oct 11, 2016 at 12:15 UTC

    The following is a comparison demonstrating 2 workers incrementing a shared counter variable. The OO interface for MCE::Shared allows for zero-locking at the application level. All 3 snippets involve set and get while incrementing the variable.

    1) ipc_shareable.pl

    use strict;
use warnings;

use IPC::Shareable;

my $options = {
   create    => 1,
   exclusive => 0,
   mode      => 0644,
   destroy   => 1,
};

tie my $cntr, 'IPC::Shareable', $options;
my $val;

$cntr = 0;

if ( ! defined ( my $pid = fork() ) ) {
   die "Cannot fork!: $!";
}
elsif ( $pid == 0 ) {
   # Child
   for ( 1 .. 10000 ) {
      ( tied $cntr )->shlock;
      $val = $cntr++;
      ( tied $cntr )->shunlock;
   }
}
else {
   # Parent
   for ( 1 .. 10000 ) {
      ( tied $cntr )->shlock;
      $val = $cntr++;
      ( tied $cntr )->shunlock;
   }

   waitpid $pid, 0;

   print "counter: ", $cntr, "\n";
}

    [download]

    2) mce_shared.pl

    use strict;
use warnings;

use MCE::Mutex;
use MCE::Shared;

my $mutex = MCE::Mutex->new();
tie my $cntr, 'MCE::Shared', 0;
my $val;

if ( ! defined ( my $pid = fork() ) ) {
   die "Cannot fork!: $!";
}
elsif ( $pid == 0 ) {
   # Child
   for ( 1 .. 10000 ) {
      $mutex->lock;
      $val = $cntr++;
      $mutex->unlock;
   }
}
else {
   # Parent
   for ( 1 .. 10000 ) {
      $mutex->lock;
      $val = $cntr++;
      $mutex->unlock;
   }

   waitpid( $pid, 0 );

   print "counter: ", $cntr, "\n";
}

    [download]

    3) mce_shared_oo.pl

    use strict;
use warnings;

use MCE::Shared;

my $cntr = MCE::Shared->scalar( 0 );
my $val;

if ( ! defined ( my $pid = fork() ) ) {
   die "Cannot fork!: $!";
}
elsif ( $pid == 0 ) {
   # Child
   for ( 1 .. 10000 ) {
      $val = $cntr->incr;
   }
}
else {
   # Parent
   for ( 1 .. 10000 ) {
      $val = $cntr->incr;
   }

   waitpid( $pid, 0 );

   print "counter: ", $cntr->get, "\n";
}

    [download]

    Results

    time in seconds  :  FreeBSD  Linux  Mac OSX

ipc_shareable.pl :   1.80    1.87    1.79
mce_shared.pl    :   0.68    0.97    0.58
mce_shared_oo.pl :   0.38    0.73    0.41

counter: 20000

    [download]

    Fetches require more time on Linux than BSD-based OS in regards to sockets. This is seen not only with Perl/MCE::Shared but also with other languages. I'm not sure why.

    MCE::Shared is fully wantarray-aware and performs fetches only when requested. Sadly, that is not the case via the TIE interface. Perhaps, this is an unnecessary overhead IMHO in regards to the TIE implementation inside Perl.

    The following results were obtained by omitting fetches: e.g. $cntr++, $cntr->incr. Fortunately, stores perform similarly between BSD and Linux via the OO interface.

    time in seconds  :  FreeBSD  Linux  Mac OSX

ipc_shareable.pl :   1.77    1.86    1.61
mce_shared.pl    :   0.68    0.95    0.58
mce_shared_oo.pl :   0.19    0.17    0.16

counter: 20000

    [download]

    The above is only a glimpse of what is possible with MCE::Shared. The use of parallel data-channels (enabled automatically) for MCE, MCE::Hobo, and threads further reduce latency for the shared-manager process. Calling MCE::Shared->init(), inside the worker, enables the optimization for fork and other parallel modules.

    This has been an interesting exercise. Thank you Bloehdian for the initial post.

    Tests were conducted on a Macbook Pro laptop (Haswell architecture) OS X 10.11.6 running at 2.6 GHz 1600 MHz RAM. FreeBSD and Linux are virtual machines managed by Parallels Desktop 11.2.1.

    Regards, Mario.

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