Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask
 
PerlMonks  

Re^2: High-speed Date Formatting

by hdb (Prior)
on Jul 12, 2013 at 08:58 UTC ( #1043913=note: print w/ replies, xml ) Need Help??


in reply to Re: High-speed Date Formatting
in thread *SOLVED* High-speed Date Formatting

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;

with

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

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); }

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>


Comment on Re^2: High-speed Date Formatting
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1043913]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others lurking in the Monastery: (14)
As of 2015-07-29 13:36 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (263 votes), past polls