Day: February 18, 2005

The most efficient way to remove leading zeros from some number is add to that number 0:

      1 #! /usr/bin/perl -w

      2

      3 use strict;

      4 use Benchmark;

      5

      6 my $test = '000000000000001';

      8 timethese shift,

      9 {

     10  Add        => sub { my $num = $test; $num += 0 },

     11  Regex    => sub { my $num = $test; $num =~ s/^0+// },

     12  Sprintf    => sub { my $num = $test; $num = sprintf '%d', $num },

     13 };
	

Benchmark: timing 10000000 iterations of Add, Regex, Sprintf…
Add: 26 wallclock secs (17.68 usr + 0.06 sys = 17.74 CPU) @ 563697.86/s (n=10000000)
Regex: 48 wallclock secs (38.32 usr + 0.09 sys = 38.41 CPU) @ 260348.87/s (n=10000000)
Sprintf: 43 wallclock secs (34.78 usr + 0.10 sys = 34.88 CPU) @ 286697.25/s (n=10000000)

Recently I’ve decided to repalce using substr by unpack when I need to split data which are presented in a row with specified order. But after that I’ve made a test to see what way is the most efficient.
The test displays that unpack is slower than substr about 30%! But on the other hand unpack makes a code more compact and clear. So, if speed is critical for you the better to use substr but if you want to make your code more readable you choise is unpack.

Continue reading unpack vs substr

Raritets of the USSR photo chronicles – Great Domestic War 1941-1945 is a set of inconceivable photos! Highly recomended!