in reply to inefficient code? works on small files ok but not larger ones

Given the simplicity and regularity of your ranges, you could simply compute indices of a two-dimensional array instead, like this: 
use strict;
use POSIX qw(floor);

my $input = $ARGV[0];
open(FILE, $input) || die "ERROR: Unable to open $input FILE for readi
+ng: $!\n";

my @range2;

my ($phi, $psi);
while (<FILE>) {
   $phi = substr($_, 0, 6);
   $psi = substr($_, 8, 6);

   print "$phi $psi\n";
   my $i = floor($phi/5.0) + 36;
   my $j = floor($psi/5.0) + 36;
   if ($i >= 0 && $j >= 0 && $i < 73 && $j < 73) {
      ++$range2[$i][$j];
   }
}

for my $i (0..72) {
   for my $j (0..72) {
      my $val = $range2[$i][$j];
      $val ||= 0;
      print "$val, ";
   }
   print "\n";
}

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Re^2: inefficient code? works on small files ok but not larger ones
by graff (Chancellor) on Oct 06, 2004 at 02:42 UTC
    I agree -- this sort of approach makes a lot more sense, and will scale very well to any amount of input. I'd just make one minor adjustment: 
    while (<FILE>) {
#  $phi = substr($_, 0, 6);
#  $psi = substr($_, 8, 6);

   ( $phi, $psi ) = split;
   ...

    [download]
    The OP didn't show us any lines of data with single-digit numbers in one or both columns. Such lines might or might not have fixed-width fields, and if not, substr() would do the wrong thing; split() would always do the right thing.

    (For that matter, it's not clear whether the column separator is two spaces or a single tab character -- again, split works in any case, while substr would get tripped up when you guess wrong about that.)

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[d/l]

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