comment on

Another small speed up can be achieved by replacing

my $leaps =  int( ($y - 1970) / 4 + 0.5 );
    (((($y-1970)*365 +$leaps+MONTHS->{$m}+($d-1))*24 +$H)*60 +$M)*60 +
+$S;
[download]

with

(((int(($y-1970)*365.25-.5)+MONTHS->{$m}+$d)*24 +$H)*60 +$M)*60 +$S;
[download]

in my experiments between 5 to 10%. All other attempts using split and unpack are much slower. I found substr to be very fast:

sub str2epoch3 {
    (((int((substr($_[0],12,4)-1970)*365.25-.5)+
     MONTHS->{substr($_[0],8,3)}+substr($_[0],5,2))*24 +substr($_[0],1
+7,2))*60 +
     substr($_[0],20,2))*60 +substr($_[0],23,2);
}
[download]

about 60% faster than BrowserUk's code. I wonder whether there is something wrong...

Here is my full code:

use strict;
use warnings;
use Benchmark qw/cmpthese/;

use constant MONTHS => { qw[
    Jan 0 Feb 31 Mar 59 Apr 90 May 120 Jun 151
    Jul 181 Aug 212 Sep 242 Oct 272 Nov 303 Dec 334
] };

sub str2epoch {
    my( $d, $m, $y, $H, $M, $S ) = $_[0] =~
        m[^.... (\d\d) (...) (\d\d\d\d) (\d\d):(\d\d):(\d\d)] 
        or die "Bad format $_[0]";      
    my $leaps =  int( ($y - 1970) / 4 + 0.5 );
    (((($y-1970)*365 +$leaps+MONTHS->{$m}+($d-1))*24 +$H)*60 +$M)*60 +
+$S;
}

sub str2epoch2 {
    my( $d, $m, $y, $H, $M, $S ) = $_[0] =~
        m[^.... (\d\d) (...) (\d\d\d\d) (\d\d):(\d\d):(\d\d)] 
        or die "Bad format $_[0]";
    (((int(($y-1970)*365.25-.5)+MONTHS->{$m}+$d)*24 +$H)*60 +$M)*60 +$
+S;
}

sub str2epoch3 {
    (((int((substr($_[0],12,4)-1970)*365.25-.5)+
       MONTHS->{substr($_[0],8,3)}+substr($_[0],5,2))*24 +substr($_[0]
+,17,2))*60 +
     substr($_[0],20,2))*60 +substr($_[0],23,2);
}

my $str = 'Fri, 01 Mar 2013 01:21:14 +0000';

cmpthese( -3, {BrowserUK => sub { str2epoch ($str) }, 
               BUK2      => sub { str2epoch2($str) }, 
               substr    => sub { str2epoch3($str) }, }
    );
</readmore>
[download]

In reply to Re^2: High-speed Date Formatting by hdb
in thread *SOLVED* High-speed Date Formatting by Endless

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


P is for Practical
	PerlMonks