Question

When I run the following script:

my @arr = [1..5000000];

for($i=0; $i<5000000; $i++) {
        $arr[$i] = $i;
        if($i % 1000000 == 0) {
                print "$i\n";
        }
}

It consumes about 500 MB memory. Used to higher-level compiled languages I would expect it to be roughly 5M * 4B = 20MB (4 bytes per number).

I guess that is because each value is a scalar, not a simple binary number. Is it possible to decrease memory footprint by treating those values as numbers, or is 500 MB for this task the only way?

Answer 1

If you are dealing with such large arrays, you might want to use a toolkit like the PDL.

(Oh, and yes, you are correct: It takes so much memory because it is an array of Perl scalars.)