comment on

Ok, so I tried Inline::C and it blows everything else away. Using the same 10 iterations, it doesn't run long enough for a decent benchmark. So changed to 100 iterations and it's under 2 seconds, where my best Perl implementation is taking 51 seconds.

Benchmark: timing 100 iterations of Inline::C, Algorithm::LUHN...
 Inline::C:  2 wallclock secs ( 1.26 usr +  0.00 sys =  1.26 CPU) @ 79.37/s (n=100)
 Algorithm::LUHN: 51 wallclock secs (51.57 usr +  0.00 sys = 51.57 CPU) @  1.94/s (n=100)



#!/usr/bin/perl
use Benchmark;
use Inline C => DATA;
my %map = map { $_ => $_ } 0..9;
# cd1 is from https://metacpan.org/pod/Algorithm::LUHN
sub cd3 {
  use integer;
  my $total = 0;
  my $flip = 1;
  foreach my $c (reverse split //, shift) {
    $c *= 2 unless $flip = !$flip;
    while ($c) {
      $total += $c % 10;
      $c = $c / 10;
    }
  }
  return (10 - $total % 10) % 10;
}
# example use:
my @range=(401135000000000..401135000099999);
timethese(100, {
    'Algorithm::LUHN' => sub { for(@range){cd3($_)} },
    'Inline::C' => sub { for(@range){cd4($_)} }
});

__END__
__C__
int cd4(char *number) {
    int i, sum, ch, num, twoup, len;
    len = strlen(number);
    sum = 0;
    twoup = 1;
    for (i = len - 1; i >= 0; --i) {
        ch = number[i];
        num = (ch >= '0' && ch <= '9') ? ch - '0' : 0;
        if (twoup) {
            num += num;
            if (num > 9) num = (num % 10) + 1;
        }
        sum += num;
        twoup = ++twoup & 1;
    }
    sum = 10 - (sum % 10);
    if (sum == 10) sum = 0;
    return sum;
}
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In reply to Re: Faster Luhn Check Digit Calculation?
by kschwab

in thread Faster Luhn Check Digit Calculation?
by kschwab



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