http://www.perlmonks.org?node_id=1138703


in reply to Re: Optimizing perl code performance
in thread Optimizing perl code performance

Update: The disparity is coming from strftime.

Update: One must use threads on the Mac and non-threads on Linux for best performance. This is mind-boggling to me. Replacing the strftime line with $A = $Y completes in a couple seconds for threads or non-threads on the Mac and Linux.

The same 500 MB input file is used by both OS.

Mac OS X Serial: 18.185s Mac OS X Parallel: 6.687s threads Mac OS X Parallel: 42.526s non-threads CentOS 7 VM Serial: 10.832s CentOS 7 VM Parallel: 23.849s threads CentOS 7 VM Parallel: 2.993s non-threads
#!/usr/bin/perl use strict; use warnings; use threads; # Comment out threads for child processes use POSIX qw(strftime); use MCE::Loop; use MCE::Candy; my $mutex :shared = 0; my $infile = $ARGV[0]; my $outfile = $ARGV[1]; open(DATAOUT, ">", $outfile); ## Workers process chunks in parallel until completed. ## Output order is preserved via MCE::Candy::out_iter_fh MCE::Loop::init { chunk_size => "2m", max_workers => 4, use_slurpio => 1, gather => MCE::Candy::out_iter_fh(\*DATAOUT) }; mce_loop_f { my ($mce, $chunkRef, $chunkID) = @_; my ($output, @Fields, $X, $Y, $A, $B, $C, $D, @G) = (""); open my $CHUNKIN, "<", $chunkRef; while( my $line = <$CHUNKIN> ) { chomp $line; @Fields = split(',', $line, 9); $X = $Fields[8]; $Y = substr $X, 0, 10; @G = gmtime $Y; $A = strftime "%M,%Y,%m,%d,%H,%j,%W,%u,%A", @G; $B = substr($A, 0, index($A, ',')); $C = int($B/5); $D = int($B/15); $output .= $line.",$Y,$A,$C,$D\n"; } close $CHUNKIN; MCE->gather($chunkID, $output); } $infile; close(DATAOUT);