in reply to How to Run Script for Multiple Files in Parallel?

you can use module Proc::Queue, that also limits the number of processes running simultaneously. 
use Proc::Queue size=>5, qw(run_back);

for (@ARGV) {
     run_back { run_code($_) };
}

1 while wait != -1;

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Re^2: How to Run Script for Multiple Files in Parallel?
by monkfan (Curate) on Apr 18, 2005 at 16:17 UTC
    Thanks Salva,

    I tried your module. It's easy to use indeed.
    BTW how can we verify that they are actually running in parallel? I tried "top" but it only shows one instances.

    Regards,
    Edward
[reply]
      To see what is happening you can use Proc::Queue trace mode, just add to your script... 
      use Proc::Queue qw(run_back);
Proc::Queue::trace(1);

      [download]
      Also, wrap the forked code inside an eval block and report errors: 
      run_back {
  eval { ... parallel code here ... };
  print STDERR $0."[$$]: $@\n" if $@;
};

      [download]
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        I tried this: 
        use Proc::Queue size=>2, qw(run_back);
Proc::Queue::trace(1);

my @ARGV = ("file1.fasta","file2.fasta");

for ( @ARGV  )
{  run_back
   {
      eval{  run_code($_) };
      print STDERR $0."[$$]: $@\n" if $@;
   }

}
1 while wait != -1;

run_code {
  my $file = shift;
  #do the rest
}

        [download]
        It gives this: 
        Proc::Queue::run_back(CODE(0x824a9d0)) called at mycode_itr.pl line 37
Proc::Queue::fork called at mycode_itr.pl line 37
Proc::Queue::run_back(CODE(0x824a9d0)) called at mycode_itr.pl line 37
Proc::Queue::fork called at mycode_itr.pl line 37
Proc::Queue::wait called at mycode_itr.pl line 38

        [download]
        Is it correct or is it an error message? If correct, what does it mean? However, now it does show 2 instances under "top".
        Regards,
        Edward
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