Re^2: Hobo with a bit of recursion

[Veltro]

Hello marioroy,

Thanks for your excellent reply. Besides giving me a couple of very nice examples you also explained sharing to me and the importance of it. I start to see now that I definitively need to do some more studying regards this subject.

One of your answers (in italic below) leads me to another question regards sharing nested objects

>> "The tie statement does not deeply share key-values during construction. The way to shared nested hash/array structures is explicitly via the STORE method"

In case objects are shared that do not have STORE and FETCH methods, and they have nested methods and objects, does this mean that the methods cannot be reached and the objects don't get to be shared?

Example, Bar object has nested Foo object (inside hash key nestedFoo):

Foo and Bar definitions:

BEGIN {
    package Foo ;
    use strict ;
    use warnings ;
    sub new {
        my $class = shift ;
        my $this = {
            _var => 1,
        } ;
        bless $this, $class ;
    }
    sub task {
        # Long operation task Foo ~ 2 seconds
        my $this = shift ;
        print "Starting task Foo for $_[0]\n" ;
        sleep(2) ;
        ++$this->{ _var } ;
        print "Finished task Foo for $_[0]\n" ;
    }
    package Bar ;
    use strict ;
    use warnings ;
    sub new {
        my $class = shift ;
        # This is not very realistic code.
        # here it is just used as an
        # example to create an object that
        # contains a nested object
        my $this = {
            _var => 1,
        } ;
        $this->{ nestedFoo } = $_[0] ;
        bless $this, $class ;
    }
    sub task {
        # Long operation task Bar ~ 6 seconds
        my $this = shift ;
        print "Starting task Bar for $_[0]\n" ;
        sleep(6) ;
        ++$this->{ _var } ;
        print "Finished task Bar for $_[0]\n" ;
    }
}

Main:

package main ;
use strict ;
use warnings ;
use MCE::Shared ;
use Data::Dumper ;

my $foo = new Foo ;
my $bar = new Bar( $foo ) ;

# my $barShared = MCE::Shared->share( { module => 'Bar' }, $foo ) ;
# or
# from examples: my $ob = MCE::Shared->share( $blessed_object );
my $barSh = MCE::Shared->share( Bar->new( $foo ) ) ;
print Dumper( $barSh->export ) . "\n" ;
$barSh->task( 'Bar' ) ; # OK
$barSh->{ nestedFoo }->task( 'Foo' ) ; # Not a HASH reference
# Program died here
$barSh->export->{ nestedFoo }->task( 'Foo' ) ; # OK, but not shared?
__END__
$VAR1 = bless( {
                 '_var' => 1,
                 'nestedFoo' => bless( {
                                         '_var' => 1
                                       }, 'Foo' )
               }, 'Bar' );

Starting task Bar for Bar
Not a HASH reference at testHobo3.pl line 60, <__ANONIO__> line 1.
Finished task Bar for Bar

Is there a way to 'get' the nestedFoo in shared context?

Is there a way to execute task for Foo without export?

edit: I forgot to mention the nested _var in each of the objects. What I mean with 'shared context' is that each _var become 2 inside of the share after the task methods have been executed.

[marioroy]

Greetings Veltro,

Yet another interesting use case :)

Q & A

In case objects are shared that do not have STORE and FETCH methods, and they have nested methods and objects, does this mean that the methods cannot be reached and the objects don't get to be shared?

Is there a way to 'get' the nestedFoo in shared context?

Is there a way to execute task for Foo without export?

For shared objects, think of them as having an entry point into the shared-manager process. Important for shared-objects, in the case of MCE::Shared, is to pass arguments instead of dereferencing. Please note that calling a method on a shared-object is executed by the shared-manager where the data resides. For this use case, embed the shared-data object inside the class. That will allow workers to run in parallel and update shared-data accordingly.

Demo 1: via Perl-like behavior

Shown with mutex in the event multiple workers update the same key. Like in the prior post, the reason is because ++ involves two trips to the shared-manager process { FETCH and STORE }. I added an export routine to filter out the mutex handle.

use strict;
use warnings;

package Foo {
    use MCE::Shared ;
    sub new {
        my $class = shift ;
        my $this  = { } ;
        tie my %data, 'MCE::Shared', _var => 1 ;
        $this->{ _SHARED_DATA } = \%data ;
        $this->{ _MUTEX } = MCE::Mutex->new ;
        bless $this, $class ;
    }
    sub task {
        # Long operation task Foo ~ 2 seconds
        my $this = shift ;
        print "Starting task Foo for $_[0]\n" ;
        sleep 2 ;
        $this->{ _MUTEX }->enter( sub {
            ++$this->{ _SHARED_DATA }{ _var } ;
        }) ;
        print "Finished task Foo for $_[0]\n" ;
    }
    sub export {
        my $this  = shift ;
        my %clone = %{ $this } ;
        delete $clone{ _MUTEX } ;
        return \%clone ;
    }
} ;

package Bar {
    use MCE::Shared ;
    use Scalar::Util 'blessed' ;
    sub new {
        my $class = shift ;
        # This is not very realistic code.
        # here it is just used as an
        # example to create an object that
        # contains a nested object
        my $this = { nestedFoo => $_[0] } ;
        tie my %data, 'MCE::Shared', _var => 1 ;
        $this->{ _SHARED_DATA } = \%data ;
        $this->{ _MUTEX } = MCE::Mutex->new ;
        bless $this, $class ;
    }
    sub task {
        my $this = shift ;
        if ( @_ == 2 ) {
            $this->{ $_[0] }->task( $_[1] ) ;
            return ;
        }
        # Long operation task Bar ~ 6 seconds
        print "Starting task Bar for $_[0]\n" ;
        sleep 6 ;
        $this->{ _MUTEX }->enter( sub {
            ++$this->{ _SHARED_DATA }{ _var } ;
        }) ;
        print "Finished task Bar for $_[0]\n" ;
    }
    sub export {
        my $this  = shift ;
        my %clone = %{ $this } ;
        delete $clone{ _MUTEX } ;
        for ( keys %clone ) {
            next unless blessed( $clone{ $_ } ) ;
            next unless $clone{ $_ }->can('export') ;
            $clone{ $_ } = $clone{ $_ }->export ;
        }
        return \%clone ;
    }
} ;

package main ;

use MCE::Hobo ;
use Data::Dumper ;

my $foo = Foo->new ;
my $bar = Bar->new( $foo ) ;

print Dumper( $bar->export ), "\n" ;

mce_async { $bar->task('Bar') } ;
mce_async { $bar->task('nestedFoo', 'Foo') } ;

MCE::Hobo->waitall ;

print "\n", Dumper( $bar->export ), "\n" ;

Demo 2: using the OO interface

This eliminates the mutex at the application level. Here, the export routine calls export on the shared-data object.

use strict;
use warnings;

package Foo {
    use MCE::Shared ;
    sub new {
        my $class = shift ;
        my $this  = { } ;
        $this->{ _SHARED_DATA } = MCE::Shared->hash( _var => 1 ) ;
        bless $this, $class ;
    }
    sub task {
        # Long operation task Foo ~ 2 seconds
        my $this = shift ;
        print "Starting task Foo for $_[0]\n" ;
        sleep 2 ;
        $this->{ _SHARED_DATA }->incr('_var') ;
        print "Finished task Foo for $_[0]\n" ;
    }
    sub export {
        my $this  = shift ;
        my %clone = %{ $this } ;
        $clone{ _SHARED_DATA } = $this->{ _SHARED_DATA }->export(
            { unbless => 1 }
        ) ;
        return \%clone ;
    }
} ;

package Bar {
    use MCE::Shared ;
    use Scalar::Util 'blessed' ;
    sub new {
        my $class = shift ;
        # This is not very realistic code.
        # here it is just used as an
        # example to create an object that
        # contains a nested object
        my $this = { nestedFoo => $_[0] } ;
        $this->{ _SHARED_DATA } = MCE::Shared->hash( _var => 1 ) ;
        bless $this, $class ;
    }
    sub task {
        my $this = shift ;
        if ( @_ == 2 ) {
            $this->{ $_[0] }->task( $_[1] ) ;
            return ;
        }
        # Long operation task Bar ~ 6 seconds
        print "Starting task Bar for $_[0]\n" ;
        sleep 6 ;
        $this->{ _SHARED_DATA }->incr('_var') ;
        print "Finished task Bar for $_[0]\n" ;
    }
    sub export {
        my $this  = shift ;
        my %clone = %{ $this } ;
        for ( keys %clone ) {
            next unless blessed( $clone{ $_ } ) ;
            next unless $clone{ $_ }->can('export') ;
            $clone{ $_ } = $clone{ $_ }->export(
                { unbless => 1 }
            ) ;
        }
        return \%clone ;
    }
} ;

package main ;

use MCE::Hobo ;
use Data::Dumper ;

my $foo = Foo->new ;
my $bar = Bar->new( $foo ) ;

print Dumper( $bar->export ), "\n" ;

mce_async { $bar->task('Bar') } ;
mce_async { $bar->task('nestedFoo', 'Foo') } ;

MCE::Hobo->waitall ;

print "\n", Dumper( $bar->export ), "\n" ;

Output

$VAR1 = {
          '_SHARED_DATA' => {
                              '_var' => 1
                            },
          'nestedFoo' => {
                           '_SHARED_DATA' => {
                                               '_var' => 1
                                             }
                         }
        };

Starting task Bar for Bar
Starting task Foo for Foo
Finished task Foo for Foo
Finished task Bar for Bar

$VAR1 = {
          '_SHARED_DATA' => {
                              '_var' => 2
                            },
          'nestedFoo' => {
                           '_SHARED_DATA' => {
                                               '_var' => 2
                                             }
                         }
        };

Regards, Mario