Beefy Boxes and Bandwidth Generously Provided by pair Networks
"be consistent"
 
PerlMonks  

Re^7: MCE segmentation fault - MCE::Flow + MCE::Channel

by marioroy (Parson)
on Mar 04, 2020 at 05:33 UTC ( #11113749=note: print w/replies, xml ) Need Help??


in reply to Re^6: MCE segmentation fault
in thread MCE segmentation fault

MCE::Channel is included in recent MCE releases. MCE::Flow allows running multiple tasks simultaneously.

So here is a great demonstration for MCE::Flow and MCE::Channel. The benefit is that the manager process does little work and better able to accommodate workers requesting input with minimum latency. The bottleneck is now the gifout task which is a separate worker. Notice user_begin and user_end called for the first task only by checking MCE->task_id. Notice also max_workers taking an array ref for specifying how many workers for each task.

The following demonstration was made possible by PerlMonks. Thanks vr for providing GD tips. Thank you Anonymous Monk for posting.

use strict; use warnings; use feature 'say'; use Imager; use MCE::Flow; use MCE::Channel; use Time::HiRes 'time'; use GD; STDOUT->autoflush; my $start = time; my $chnl = MCE::Channel->new(); my $count = 0; my $bkg; MCE::Flow->init( max_workers => [ MCE::Util::get_ncpu() - 1, 1 ], chunk_size => 1, init_relay => '', gather => sub { print "\r", $count++; }, user_begin => sub { if (MCE->task_id == 0) { $bkg = Imager->new(xsize=>800, ysize=>600); $bkg->filter(type=>"gradgen", xo=>[ 100, 300, 600 ], yo=>[ 100, 300, 100 ], colors=>[ qw(red blue green) ]); $bkg->filter(type=>"noise", amount=>12, subtype=>0) } }, user_end => sub { if (MCE->task_id == 0) { $chnl->end; } } ); sub task_frames { my ($mce, $chunk_ref, $chunk_id) = @_; my @i_data; for my $x (@{ $chunk_ref }) { my $i = $bkg-> copy; $i->string( text => $x, color => Imager::Color->new('ffffff'), font => Imager::Font->new( # file => '/usr/share/fonts/truetype/msttcorefonts/cour.ttf', # + Ubuntu # file => '/System/Library/Fonts/Courier.dfont', face => 'Courier New', # mswin size => 420, aa => 1), x => 25, y => 500, ); $i->write(data => \my $data, type => 'gif'); push @i_data, $data; MCE->gather($x); } MCE::relay { $chnl->send(\@i_data) }; } sub task_gifout { my $image; my $gifdata; while ( my $i_data_ref = $chnl->recv ) { if (!defined $gifdata) { $image = GD::Image-> newFromGifData( shift @{ $i_data_ref } ) +; $gifdata = $image-> gifanimbegin( 0,0 ); $gifdata .= $image-> gifanimadd( 1,0,0,1,1 ); } while ( my $data = shift @{ $i_data_ref } ) { my $frame = GD::Image-> newFromGifData( $data ); $gifdata .= $frame-> gifanimadd( 1,0,0,1,1 ); } } $gifdata .= $image-> gifanimend; open my $fh, '>:raw', 'gd.gif'; print $fh $gifdata; close $fh; } mce_flow \&task_frames, \&task_gifout, [ 0 .. 319 ]; MCE::Flow->finish; print " frame GIF done!\n"; printf "compute time: %0.3fs\n", time - $start;

There is a lot of parallel going on :) Although workers complete sooner, the manager process still waits for all tasks to finish before MCE::Flow exits.

Regards, Mario

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://11113749]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others taking refuge in the Monastery: (6)
As of 2020-10-01 08:45 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    If at first I donít succeed, I Ö










    Results (177 votes). Check out past polls.

    Notices?