Running perl threads in loop

[dvinay]

hi,

I want to run perl threads in an For loop, for example suppose, i create 2 threads each containing an command to execute, once these 2 threads are completed i need to another set of same 2 threads and run it, and this should go on for the number of times i have given as an input to the main script below is the small code snippet

my @threads; #---Making Concurrent OneClick backup commands using threads------#

        
for (my $i=0;$i<=3;$i++)
{
        #-----performing the CHO loops as given by user-------#
        
            foreach (@finalOneClickarray) {
               push @threads, threads->new(\&concurrentBackupCommandsR
+ead, $_);
            }
       
            foreach (@threads) {
               $_->join();
            }

}

sub concurrentBackupCommandsRead()
{

   doing my stuff here.........
}

i have tried to put for loop, but it errors out saying Perl exited with active threads: please let me know what am i doing wrong here

[NetWallah]

Here is sample working code showing how your work could be implemented (based on my understanding of your text):


#!/usr/bin/perl
use strict;
use warnings;
use threads;
#use threads::shared;

print "Starting main program\n";
my $MAXTHREADS=5;
my @work= map{int(rand()*1000)} 1..rand()*200;
print "Work to do: " , scalar(@work) , " entries:\n\t@work\n\n";

my (@threads);
my $workstart= 0;
my $workincrement  = int((scalar(@work) + $MAXTHREADS - 1) / $MAXTHREA
+DS );
for my $CurrentThreadNumber (1..$MAXTHREADS) {
        my $t = threads->new(\&sub1, $CurrentThreadNumber, $workstart,
+ $workstart+$workincrement);
        $workstart +=$workincrement+1;
        push(@threads,$t);
}
foreach (@threads) {
        $_->join;
}
print "End of main program\n";

sub sub1 {
   my ($thn,$workstart, $workend)=@_;
   $workend =$#work if $workend > $#work;
   print "in Thread $thn starting $workstart  Till  $workend\n";
   print "($thn: $work[$_]) " for $workstart..$workend;
   print "\n";
   sleep rand() * 10;
   print "Exiting  Thread $thn\n";
}

Update: Handling the edge case where scalar(@work) <= $MAXTHREADS is left as an exercise.

[BrowserUk]

please let me know what am i doing wrong here

One thing you are doing wrong is that @threads will retain the handles from threads created during the first iteration of the loop, for every subsequent iteration.

Try moving its declaration inside the loop.

[CountZero]

Please put your code in <code> ... </code>-tags. That makes it much easier to read your code and test it.

[dvinay]

Sorry for my mistake, i know i haven't followed the rules, now i have updated my code snippet, please let me know what is that wrong i am doing here

Thanks, Vinay

[Anonymous Monk]

A much better design is to spawn threads which accept requests from some sort of queue and process them repeatedly ... remaining alive the entire time. A thread is not a subroutine, even though it runs one.