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I have a matrix that I want to randomize a couple of thousand times, while keeping the row and column totals the same: 1 2 3 A 0 0 1 B 1 1 0 C 1 0 0 An example of a valid random matrix would be: 1 2 3 A 1 0 0 B 1 1 0 C 0 0 1 My actual matrix is a lot bigger (about 600x600 items), so I really need an approach that is computationally efficient. My initial (inefficient) approach consisted of shuffling arrays using the Perl Cookbook shuffle I pasted my current code below. I've got extra code in place to start with a new shuffled list of numbers, if no solution is found in the while loop. The algorithm works fine for a small matrix, but as soon as I start scaling up it takes forever to find a random matrix that fits the requirements. Is there a more efficient way to accomplish what I'm searching for? Thanks a lot! #!/usr/bin/perl -w use strict; my %matrix = ( 'A' => {'3' => 1 }, 'B' => {'1' => 1, '2' => 1 }, 'C' => {'1' => 1 } ); my @letters = (); my @numbers = (); foreach my $letter (keys %matrix){ foreach my $number (keys %{$matrix{$letter}}){ push (@letters, $letter); push (@numbers, $number); } } my %random_matrix = (); &shuffle(\@numbers); foreach my $letter (@letters){ while (exists($random_matrix{$letter}{$numbers[0]})){ &shuffle (\@numbers); } my $chosen_number = shift (@numbers); $random_matrix{$letter}{$chosen_number} = 1; } sub shuffle { my $array = shift; my $i = scalar(@$array); my $j; foreach my $item (@$array ) { --$i; $j = int rand ($i+1); next if $i == $j; @$array [$i,$j]

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