What i don't understand in your code is what the purpose of this is meant to be: 
my $tiles_for_rx = $tiles[$rx];

[download]
My understanding is that this dumps the size of $tiles[$rx] in $tiles_for_rx, due to being a multi-dimensional array. I may be wrong there, but the debugger seems to agree.

However my understanding or lack of is not the point here. The point is that your variant did not work in the live when applied to my code. This works: 
my ($rx,$ry,$y,$x,$xScaled);

my $bxScaled = $bx * 16;
my $byScaled = $by * 16;
my $tile_index=0;

my (@realx,@realy);

my ($tile);

for $x ( 0..15 ) {
    $rx = $bxScaled+$x;
    my $tile = \$tiles[$bz][type][$rx];
    
    for $y ( 0..15 ) {
        $ry = $byScaled+$y;
        
        if (
            !defined $$tile->[$ry] ||
            $$tile->[$ry] != $type_data[$tile_index]
        ) {
            $changed = 1;
            $$tile->[$ry] = $type_data[$tile_index];
        }
        ++$tile_index;
    }
}

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When i try to refactor it to look like your example, it doesn't. Now mind you, i may be making some kind of mistake somewhere, but i'm fairly sure that your variant can't work. Feel free to correct me if i am making a mistake.

In reply to Re^5: How to speed up a nested loop? by Xenofur
in thread How to speed up a nested loop? by Xenofur

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