The serial solution by aitap seems fast enough. I was curious and wanted to see if running faster is possible against a 200 MB input file. The serial version completes in 4.566 seconds and parallel in 1.440 seconds, which is beyond 3x faster.

Perl regular expressions involves CPU time and the reason for running faster. IO is sequential in MCE, not parallel or random, to minimize unnecessary delays; e.g. seek time.

Perl is fast at these things :)

use warnings;
use strict;

use MCE::Loop;
use MCE::Candy;

## Select input and output files
my $input_file  = 'InputFile.OH1';
my $output_file = 'OutputFile.csv';

open my $ofh, ">", $output_file
   or die "cannot open '$output_file' for writing: $!\n";

## Creates a header at the beginning of the file
my $header = "HEC1_ID,Q100_Base,TTP,Area\n";
print $ofh $header;

## Extracts data from input in parallel.
MCE::Loop::init {
   use_slurpio => 1, chunk_size => '20k', max_workers => 4,
   gather => MCE::Candy::out_iter_fh($ofh),
};

mce_loop_f {
   my ( $output, $mce, $chunk_ref, $chunk_id ) = ( '', @_ );

   open my $ifh, "<", $chunk_ref;
   while (<$ifh>) {
     s{
      ^             # at the beginning of the line
      \+            # followed by literal plus
      (?:\s+(\S+))  # column one
      (?:\s+(\S+))  # column two
      (?:\s+(\S+))  # column three
      (?:\s+\S+){3} # skip three columns
      \s+(\S+)$     # catch the last one, too
     }{$1,$2,$3,$4}x
      and do { $output .= $_ };
   }
   close $ifh;

   MCE->gather( $chunk_id, $output );

} $input_file;

close $ofh;

[download]

Kind regards, Mario.

In reply to Re: Extract string to file by marioroy
in thread Extract string to file by oryan

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