When I run the following code: 
#!/usr/bin/perl
use strict;
use warnings;
use AI::Genetic;
use Data::Dumper;

$|=1;
my $ga = AI::Genetic->new
  (
   -fitness => \&my_fitness,
   -type => 'rangevector'
  );

$ga->init([ [0,10], [0,10], [0,10], [0,10] ]);
$ga->sortIndividuals($ga->people());
# Note that using this instead of sortPopulation does NOT
# cause the same warnings:
# my @populace = sort {$a->score <=> $b->score} @{$ga->people()};

sub my_fitness {
  my $genes = shift;
  print ref $genes, "\n";

  my @sorted = sort {
    print Dumper($a,$b); sleep 1;
    $genes->[$a] <=> $genes->[$b]
  } 0..3;

  my $score = $sorted[1] + 2*$sorted[2] + 3*$sorted[3];

  print "DEBUG: score was $score\n";
  return $score;
}

[download]
I get 
1037% perl genetic.pl
ARRAY
$VAR1 = 0;
$VAR2 = 1;
$VAR1 = 2;
$VAR2 = 3;
$VAR1 = 1;
$VAR2 = 2;
$VAR1 = 1;
$VAR2 = 3;
$VAR1 = 0;
$VAR2 = 3;
DEBUG: score was 7
ARRAY
$VAR1 = undef;
$VAR2 = undef;
Use of uninitialized value in array element at genetic.pl line 27.
Use of uninitialized value in array element at genetic.pl line 27.
$VAR1 = undef;
$VAR2 = undef;
Use of uninitialized value in array element at genetic.pl line 27.
Use of uninitialized value in array element at genetic.pl line 27.
$VAR1 = undef;
$VAR2 = undef;
Use of uninitialized value in array element at genetic.pl line 27.
Use of uninitialized value in array element at genetic.pl line 27.
$VAR1 = undef;
$VAR2 = undef;
Use of uninitialized value in array element at genetic.pl line 27.
Use of uninitialized value in array element at genetic.pl line 27.
DEBUG: score was 14
   etc...

[download]
So the first sort seems to work fine, but it crashes on subsequent iterations. A mystery...

Update: It is an official bug: check out nested sort in perl-5.7.0 fails.

-Mark

In reply to Re: AI::Genetic gives me strange warnings by kvale
in thread AI::Genetic gives me strange warnings by fizbin

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