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Re: Parallelization of multiple nested loops

by BrowserUk (Pope)
on Feb 07, 2018 at 13:44 UTC ( #1208634=note: print w/replies, xml ) Need Help??

in reply to Parallelization of multiple nested loops

Starting a new process to construct a single string and then pass it back to the parent (and its parent and its parent...) for accumulation is crazy -- and as you know, slow.

This code produces the same data into a file in less than 1 hour:

#! perl -slw use strict; use Time::HiRes qw[ time ]; use Algorithm::Combinatorics qw[ variations_with_repetition ]; my $start = time; my @in = qw[ 0.0 0.2 0.4 0.6 0.8 1.0 ]; my $iter = variations_with_repetition( \@in, 11 ); my $c = 0; while( $_ = $iter->next ) { print join "\t", @$_, 1 , 1; ++$c; } printf STDERR "Took: %f seconds [$c]\n", time() - $start; __END__ C:\test>1208610 | wc -l Took: 3444.838110 seconds [362797056] 362797056

And you can read it from that file, one line at a time to avoid blowing your memory, in about 5 minutes.

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