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    $readset->remove($handle) if eof($handle);

    close $handle;

  } until (++$count == $np);

  return \@result;
}

sub close2 {
  my ($self, $cluster_handle) = @_;

  my $readset = $cluster_handle->get_readset();
  my @wproc = @{$cluster_handle->get_wproc()};
  my %id = %{$cluster_handle->get_id()};
  my $np = values(%id);

  my $count = 0;
  my @ready;
  my @result;

  do {
    push @ready, $readset->can_read unless @ready;

    my $handle = shift @ready;

    my $me = $id{0 + $handle};

    my ($aux, $bytes, $r);

    while ((!defined($bytes)) || ($bytes))  {
      $bytes = sysread($handle, $aux, BUFFERSIZE);
      $r .= $aux if ((defined($bytes)) && ($bytes));
    }

    $result[$me] = $r;

    $readset->remove($handle) if eof($handle);

    $handle->close();
    $wproc[$count]->close();

  } until (++$count == $np);

  return \@result;
}

1;
__END__

=head1 NAME

GRID::Cluster - Virtual clusters using SSH links

=head1 SYNOPSIS

  use GRID::Cluster;

  my $np = 4;     # Number of processes
  my $N = 1000;   # Number of iterations
  my $clean = 0;  # The files are not removed when the execution is finished

  my $machine = [ 'host1', 'host2', 'host3' ];                # Hosts
  my $debug = { host1 => 0, host2 => 0, host3 => 0 };         # Debug mode in every host
  my $max_num_np = { host1 => 1, host2 => 1, host3 => 1 };    # Maximum number of processes supported by every host

  my $c = GRID::Cluster->new(host_names => $machine, debug => $debug, max_num_np => $max_num_np);
    || die "No machines has been initialized in the cluster";

  # Transference of files to remote hosts
  $c->copyandmake(
    dir => 'pi',
    makeargs => 'pi',
    files => [ qw{pi.c Makefile} ],
    cleanfiles => $clean,
    cleandirs => $clean, # remove the whole directory at the end
    keepdir => 1,
  );

  # This method changes the remote working directory of all hosts
  $c->chdir("pi/")  || die "Can't change to pi/\n";

  # Tasks are created and executed in remote machines using the method 'qx'
  my @commands = map {  "./pi $_ $N $np |" } 0..$np-1
  print "Pi Value: ".sum @{$c->qx(@commands)}."\n";

=head1 DESCRIPTION

This module is based on the module L<GRID::Machine>. It provides a set
of methods to create 'virtual' clusters by the use of SSH links for
communications among different remote hosts.

Since main features of C<GRID::Machine> are zero administration and minimal
installation, L<GRID::Cluster> directly inherites these features.

Mainly, C<GRID::Cluster> provides:

=over

=item *

An extension of the Perl C<qx> method. Instead of a single command it receives a 
list of commands. Commands are executed - via SSH - using the master-worker paradigm.

=item *

Services for the transference of files among machines.

=back

=head1 DEPENDENCIES

This module requires these other modules and libraries:

=over

=item * L<GRID::Machine> module by Casiano Rodriguez Leon

=item * L<Term::Prompt> module by Allen Smith