ID: 48828
Updated by: [email protected]
Reported By: php at richardneill dot org
-Status: Open
+Status: Feedback
Bug Type: Performance problem
Operating System: Linux
PHP Version: 6CVS-2009-07-07 (CVS)
New Comment:
Have you set your timezone in your php.ini? I don't see it set in your
script. And is this actually PHP6?
Previous Comments:
------------------------------------------------------------------------
[2009-07-07 05:05:12] php at richardneill dot org
Description:
------------
I've just been troubleshooting a script whose job is to fix
logfiles. Each line of the logfile has a timestamp, but only
HH:MM:SS and it's missing the date. My script has to fix this.
For a 500,000 line file, this takes about 2 minutes, so I
investigated further. I found that strtotime() was really quite a
lot slower than I expected, and that using preg_match() instead
doubled the script execution speed.
Is this really to be expected, or could strtotime() be optimised?
Reproduce code:
---------------
#!/usr/bin/php
<?
//This demonstrates that strtotime() is really rather slow. The
//example is quite contrived, but surely it should be possible to
//make strtotime() much faster than an entire regular-expression
//match, rather than 3 times slower?
$time1=microtime(1);
$timestamp1="05:03:02";
$timestamp2="03:05:07";
for ($i=0;$i<1E6;$i++){
$seconds = strtotime($timestamp1) - strtotime($timestamp2);
#echo "$seconds\n"; //Do something with $seconds
}
$time2=microtime(1);
for ($i=0;$i<1E6;$i++){
//preg_match lets us both check that this IS a valid
//timestamp and split it into parts.
preg_match('/^(\d\d):(\d\d):(\d\d)(\.\d+)?$/', $timestamp1,
$matches1);
preg_match('/^(\d\d):(\d\d):(\d\d)(\.\d+)?$/', $timestamp2,
$matches2);
$seconds = ( 3600 * intval($matches1[1]) + 60 *
intval($matches1[2]) + intval($matches1[3]) ) -
( 3600 * intval($matches2[1]) + 60 *
intval($matches2[2]) + intval($matches2[3]) );
#echo "$seconds\n"; //Do something with $seconds
}
$time3=microtime(1);
# 42.8 on 2.4GHz CPU
echo "Each pair of calls to strtotime() took:".($time2 - $time1 )."
microseconds \n";
# 16.6.
echo "Each pair of calls to preg_match() etc took:".($time3 - $time2
)." microseconds \n";
?>
Expected result:
----------------
I expect strtotime(), which is designed specifically for the
purpose, to be faster than preg_match, which is more
general-purpose.
Actual result:
--------------
strtotime() takes about 3 x longer than the brute-force approach
using a regular-expression + array maths. Is that really expected?
date() isn't very fast either.
42us means 100,000 CPU cycles!
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=48828&edit=1
