Update: The time is 2.2 seconds using the same demonstration below on a Mac running the upcoming MCE 1.706 release. Running with four workers also completes in 2.2 seconds. Basically, have reached the the underlying hardware limitation.

Today, I looked at MCE to compare against the 2 GB plain text file residing in FS cache and not. Increasing the chunk_size value is beneficial, especially when the file does not exists in OS level FS cache.

With an update to the code, simply by increasing the chunk_size value from '1m' to '24m', the total time now takes 3.2 seconds to complete.

use strict;
use warnings;

use MCE::Flow;
use MCE::Shared;

my $counter1 = MCE::Shared->scalar( 0 );
my $counter2 = MCE::Shared->scalar( 0 );

mce_flow_f {
   chunk_size => '24m', max_workers => 8,
   use_slurpio => 1,
},
sub {
   my ( $mce, $chunk_ref, $chunk_id ) = @_;

   my $numlines = $$chunk_ref =~ tr/\n//;
   my $occurances = () = $$chunk_ref =~ /123456\r?$/mg;

   $counter1->incrby( $numlines );
   $counter2->incrby( $occurances );

}, "Dictionary2GB.txt";

print "Num lines : ", $counter1->get(), "\n";
print "Occurances: ", $counter2->get(), "\n";

[download]

One day, I will try another technique inside MCE to see if IO performance can be improved upon.

Resolved.

In reply to Re: How to optimize a regex on a large file read line by line ? by marioroy
in thread How to optimize a regex on a large file read line by line ? by John FENDER

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