Perl在并行化后打印嵌套循环输出时出现问题

Question

I'm trying to print output of the following code , but there is something wrong with it, some lines do not have 5 columns, some values are missing, mixed , ....

./script.pl file 5 0.00 0.021

#!/usr/bin/perl

use warnings;
use strict;

use Parallel::ForkManager;

my $outputfilename = $ARGV[0];
my $CPU_count      = $ARGV[1];
my $start          = $ARGV[2];
my $end            = $ARGV[3];


my $fork_manager = Parallel::ForkManager->new($CPU_count);

for ( my $k1 = $start; $k1 < $end; $k1 += 0.001 ) {

    $fork_manager->start and next;

    for ( my $k2 = $start; $k2 < $end; $k2 += 0.01 ) {
        for ( my $k3 = $start; $k3 < $end; $k3 += 0.001 ) {
            for ( my $k4 = $start; $k4 < $end; $k4 += 0.001 ) {
                for ( my $k5 = $start; $k5 < $end; $k5 += 0.001 ) {

open my $F1, '>',$outputfilename . "_" . $k1 . $k2 . $k3 . $k4 . $k5  or die $!;
         print  $F1 ("k1: $k1\tk2: $k2\tk3: $k3\tk4: $k4\tk5: $k5\n");

                }
            }
        }
    }
    $fork_manager->finish;
}
$fork_manager->wait_all_children;

incorrect output

...
k1: 0.002   k2: 0.00    k3: 0.00    k4: 0.016   k5: 0.006
k1: 0.002   k00 k2: 0.00    k3: 0.001   k4: 0.012   k5: 0.003
k1: 0.003   k2: 0.00    k3: 0.012   k4: 0.013   k5: 0.001
k1: 0.003   k2: 0.00    k3: 0.012   0.011
....

Thank you very much for your help!

Answer 1

Your forks are racing to write to file. Depending on what you want from your output, you should place exclusive file locks on strategic points.

In example below at least lines won't get mixed up.

 use Fcntl qw(:flock);

 # ...
 flock($F1, LOCK_EX) or die $!;
 print $F1 ("k1: ",$k1,"\t","k2: ",$k2,"\t","k3: ",$k3,"\t","k4: ",$k4,"\t","k5: ",$k5,"\n");
 flock($F1, LOCK_UN);

Answer 2

for ( my $k1 = $start; $k1 < $end; $k1 += 0.001 ) {

    $fork_manager->start and next;
    open ( my $output, ">", $outputfilename."_".$k1 ) or die $!;
    for ( my $k2 = $start; $k2 < $end; $k2 += 0.01 ) {
        for ( my $k3 = $start; $k3 < $end; $k3 += 0.001 ) {
            for ( my $k4 = $start; $k4 < $end; $k4 += 0.001 ) {
                for ( my $k5 = $start; $k5 < $end; $k5 += 0.001 ) {
                    print  {$output} ("k1: $k1\tk2: $k2\tk3: $k3\tk4: $k4\tk5: $k5\n");
                }
            }
        }
    }
    close ( $output );
    $fork_manager->finish;
}
$fork_manager->wait_all_children;


foreach ( my $filename, glob ( "$outputfilename_*" ) ) {
     #stick together the results of something. 
}

You'll end up with one file per fork - so from 0..1 you'll get 1000. But each fork will have one active output filehandle, so no race condition.