sub make_config {
  my (@genes) = @_;
  # sort classes in order by genes:
  use Data::Dumper;
  my (@order) = sort {$genes[$a] <=> $genes[$b];} (0..$#CLASSES);
  my (@sclasses) = @CLASSES[@order];
  push(@sclasses, (qw{XXX}) x ($SLOTS * $ROOMS));
  my ($config) = [];
  for my $s (0..$SLOTS-1) {
	push @$config, [];
	for my $r (0..$ROOMS-1) {
	  my $i=0;
	  while (!is_acceptable($sclasses[$i],$s,$r,$config)) {$i++;}
	  push @{$config->[-1]}, splice(@sclasses,$i,1);
	}
  }
  $config;
}