VERSION
This document describes MCE::Relay version 1.608SYNOPSIS
use MCE::Flow;
my $file = shift || \*STDIN;
## Line Count #######################################
mce_flow_f {
use_slurpio => 1, init_relay => 0,
},
sub {
my ($mce, $slurp_ref, $chunk_id) = @_;
my $line_count = ($$slurp_ref =~ tr/\n//);
## Receive and pass on updated information.
my $lines_read = MCE::relay { $_ += $line_count };
}, $file;
my $total_lines = MCE->relay_final;
print {*STDERR} "$total_lines\n";
## Orderly Action ###################################
mce_flow_f {
use_slurpio => 1, init_relay => 0,
},
sub {
my ($mce, $slurp_ref, $chunk_id) = @_;
## Exclusive access to STDOUT. Relays 0.
MCE::relay { print $$slurp_ref };
}, $file;
DESCRIPTION
This module enables workers to receive and pass on information orderly with zero involvement by the manager process while running. The module is loaded automatically when init_relay is specified.All workers must participate when relaying data. Calling relay more than once is not recommended inside the block. Doing so will stall the application.
Relaying is not met for passing big data. The last worker will likely stall if exceeding the buffer size for the socket. Not exceeding 8 KiB is safe across all platforms.
API DOCUMENTATION
- MCE->relay ( sub { code } )
- MCE::relay { code }
-
Relay is enabled by specifying the init_relay option which takes a hash or array
reference, or a scalar value. Relaying is orderly and driven by chunk_id when
processing data, otherwise task_wid. Omitting the code block (e.g. MCE::relay)
relays forward.
Below, relaying multiple values via a HASH reference.
use MCE::Flow max_workers => 4; mce_flow { init_relay => { p => 0, e => 0 }, }, sub { my $wid = MCE->wid; ## do work my $pass = $wid % 3; my $errs = $wid % 2; ## relay my %last_rpt = MCE::relay { $_->{p} += $pass; $_->{e} += $errs }; MCE->print("$wid: passed $pass, errors $errs\n"); return; }; my %results = MCE->relay_final; print " passed $results{p}, errors $results{e} final\n\n"; -- Output 1: passed 1, errors 1 2: passed 2, errors 0 3: passed 0, errors 1 4: passed 1, errors 0 passed 4, errors 2 final
Or multiple values via an ARRAY reference.
use MCE::Flow max_workers => 4; mce_flow { init_relay => [ 0, 0 ], }, sub { my $wid = MCE->wid; ## do work my $pass = $wid % 3; my $errs = $wid % 2; ## relay my @last_rpt = MCE::relay { $_->[0] += $pass; $_->[1] += $errs }; MCE->print("$wid: passed $pass, errors $errs\n"); return; }; my ($pass, $errs) = MCE->relay_final; print " passed $pass, errors $errs final\n\n"; -- Output 1: passed 1, errors 1 2: passed 2, errors 0 3: passed 0, errors 1 4: passed 1, errors 0 passed 4, errors 2 final
Or simply a scalar value.
use MCE::Flow max_workers => 4; mce_flow { init_relay => 0, }, sub { my $wid = MCE->wid; ## do work my $bytes_read = 1000 + ((MCE->wid % 3) * 3); ## relay my $last_offset = MCE::relay { $_ += $bytes_read }; ## output MCE->print("$wid: $bytes_read\n"); return; }; my $total = MCE->relay_final; print " $total size\n\n"; -- Output 1: 1003 2: 1006 3: 1000 4: 1003 4012 size
- MCE->relay_final ( void )
-
Call this method to obtain the final relay values after running. See included
example findnull.pl for another use case.
use MCE max_workers => 4; my $mce = MCE->new( init_relay => [ 0, 100 ], ## initial values (two counters) user_func => sub { my ($mce) = @_; ## do work my ($acc1, $acc2) = (10, 20); ## relay to next worker MCE::relay { $_->[0] += $acc1; $_->[1] += $acc2 }; return; } )->run; my ($cnt1, $cnt2) = $mce->relay_final; print "$cnt1 : $cnt2\n"; -- Output 40 : 180
- MCE->relay_recv ( void )
-
The relay_recv method allows one to perform an exclusive action prior to
relaying. Below, the user_func is taken from the cat.pl example. Relaying
is chunk_id driven (or task_wid when not processing input), thus orderly.
user_func => sub { my ($mce, $chunk_ref, $chunk_id) = @_; if ($n_flag) { ## Relays the total lines read. my $output = ''; my $line_count = ($$chunk_ref =~ tr/\n//); my $lines_read = MCE::relay { $_ += $line_count }; open my $fh, '<', $chunk_ref; $output .= sprintf "%6d\t%s", ++$lines_read, $_ while (<$fh>); close $fh; $output .= ":$chunk_id"; MCE->do('display_chunk', $output); } else { ## The following is another way to have ordered output. Workers ## write directly to STDOUT exclusively without any involvement ## from the manager process. The statements between relay_recv ## and relay run serially and most important orderly. ## STDERR/OUT flush automatically inside worker threads and ## processes. Disable buffering on file handles otherwise. MCE->relay_recv; ## my $val = MCE->relay_recv; ## relay simply forwards 0 below print $$chunk_ref; ## exclusive access to STDOUT ## important, flush immediately MCE->relay; } return; }
INDEX
MCEAUTHOR
Mario E. Roy, <marioeroy AT gmail DOT com>