The major missing feature is that at present there's no way to get it to run cmd -x arg1, cmd -x arg2...; there's no way to get the constant -x in there.
I tried fixing it by changing: 
my $cmd = shift;

[download]
to: 
my @cmd = split /\s+/, shift;

[download]
and: 
$pid{spawn($cmd, split /\s+/, shift @ARGV)} = 1;

[download]
to: 
$pid{spawn(@cmd, shift @ARGV)} = 1;

[download]
(I also decided that splitting the remaining arguments was a fairly dumb mistake, so got rid of that.)

Now, to get it to run cmd -x arg1, cmd -x arg2...; you just runN "cmd -x" arg1 arg2... .

I think this has worked out pretty well in practice so far, but only time will tell.

Complete code is now:

#!/usr/bin/perl

use Getopt::Std;
my %opt = (n => 1);
getopts('r:n:v', \%opt) or usage();

my @cmd = split /\s+/, shift;
@ARGV = shuffle(@ARGV) if $opt{r};

my %pid;
while (@ARGV) {
  if (keys(%pid) < $opt{n}) {
    $pid{spawn(@cmd, shift @ARGV)} = 1;
  } else {
    delete $pid{wait()};
  }
}

1 while wait() >= 0;

sub spawn {
  my $pid = fork;
  die "fork: $!" unless defined $pid;
  return $pid if $pid;
  warn "@_\n" if $opt{v};
  exec @_;
  die "exec: $!";
}

sub usage {
  print STDERR "Usage: $0 [-n N] [-r] [-v] command arg1 arg2...
Run command arg1, command arg2, etc., concurrently.
Run no more than N processes simultaneously (default 1)
    -r: run commands in random order instead of specified order (unimp
+l.)
    -v: verbose mode
";
  exit 1;
}

[download]

--
Mark Dominus
Perl Paraphernalia

In reply to Re^3: Parallelization of heterogenous (runs itself Fortran executables) code by Dominus
in thread Parallelization of heterogenous (runs itself Fortran executables) code by Jochen

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