Dear Monks, I need to parallelize the process of finding positions of various patterns which has been collected and stored into a hash (refer the script which i have attached). if I dont parallelized the process of find patterns stored in a hash then all patterns has to stay in the queue until the preceding pattern is completed. So here I dont know whether to use threads or forks for achieving parallelization.

I have attached my script, where I have tried to implement perl ithreads to accomplish the parallelization (at line 25, inside the foreach loop). I dont think that the threads I have implemented works properly, because there's no visible improvement in the script as used without threads.

here in this paragraph, i have tried to explain the objective of my work. i get in a string and break it down into a length specified substrings (which may vary) and find the positions of those substrings.

use threads ;
use feature "say";
use warnings;

my $input_file = "text";                #Contains a single lined strin
+g without any newline character
open my $hd, "<", $input_file or die "Couldn't open '$input_file' - $!
+";
my $text=<$hd>;
chomp($text);

my $window=5;                        #Length of the window
my $i=0;
LOOP:seek $hd,$i,0;                    #Here seek and read give us the
+ first $window lengthed substing runned over loop
read ($hd,my $substring,$window);
my %hash;
if(length($substring)==$window)                
{
    $hash{$substring}=$i;                #$substring pushed into a has
+h, here I have avoided array has there may be repeated substrings in 
+the $text
    $i++;
    goto LOOP;
}

my $count = keys %hash;
my $j=0;

foreach my $pattern (keys %hash)
{
    if($j<=$count)
    {
        my $thr="thread".$j;
        $$thr=threads->create(\&position,$text,$pattern);
        $j++;
    }
}

for($ii=0;$ii<=$count;$ii++)
{
    $thr="thread".$ii;
    print $thr,"\n";
    $$thr->join();
}

sub position
{
    my ($text,$pattern) = @_ ;
    
    my $offset = 0;

    print "\n$pattern ($window)\n";
    print '~' x $window,"\n";
    
    my $pos=index $text,$pattern,$offset;
    
    while ($pos != -1) 
    {
        print $pos+1," to ",$pos+$window,"\n";
        $offset = $pos + 99;
        $pos = index($text, $pattern, $offset);
    }
}

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In reply to Trouble implementing threads by saranrsm

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