As long as this thread has gotten so popular, I'll throw in my 2 cents + TMTOWTDI. No matter what your final intent is, the problem you've presented is just shredding a space-delimited file (as pointed out by JavaFan and jethro). I present my solution:

use strict;
use warnings;

my (@A, @IA, @JA) = ();
while (<DATA>) {
    chomp;
    my @elements = split /\s+/;
    my $i = 0;
    my $new_line = 1;
    while (defined(my $element = shift @elements)) {
        $i++;
        if ($element) {
            push @A, 0 + $element;
            if ($new_line) {
                push @IA, scalar @A;
                $new_line = 0;
            }
            push @JA, $i;
        }
    }
}
push @IA, 1 + @A;
print('@A  = [', join(" ", @A), "]\n");
print('@IA = [', join(" ", @IA), "]\n");
print('@JA = [', join(" ", @JA), "]\n");


__DATA__
1 2 0 0
0 3 9 0
0 1 4 0

[download]

As a side note, if you are planning on doing actual math on the results, you should plan on using seriously optimized math libraries (read LAPACK, ATLAS, Intel mkl...)

In reply to Re: Memory Efficient Sparse Matrix Handling by kennethk
in thread Memory Efficient Sparse Matrix Handling by neversaint

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