On Fri, July 20, 2007 4:16 am, Colin Guthrie wrote:
> Sancar Saran wrote:
>> Another simple performance tip.
>>
>> Most of for examples of php look like this
>> for($x=0;$x<sizeof($arrSometing);$x++)
>>
>> This is bad. In every cycle you call sizeof
>>
>> this was good
>> $intSize = sizeof($arrSometing);
>> for($x=0;$x<$intSize;$x++)
>>
>> if u use.
>> for($x=0;$x<$intSiz;++$x). You may gain another %10
>>
>> to determine costs of your functions use xdebug and kcachegrind.
>
> I've always used pre-increment in loops like you suggest as it was an
> ingrained part of my C/C++ learning from a performance perspective. I
> wasn't sure if the same was true in PHP but you seem to suggest it is,
> so I feel justified now :)
I don't really care if one uses pre or post, but I just benchmarked
this, and I don't really think it makes a 10% win.
And I had to crank it up to 10 MILLION to get any kind of realistic
measurable time in the first place.
How often do you have a PHP loop that runs to 10 MILLION iterations?!
Note that I did three with pre before post tests and three post before
pre tests to even out any caching effects.
Test environment details at the bottom.
sagacitydev@ch10106cus002 ~/junk $ cat pre.php post.php
<?php
for ($i = 0; $i < 10000000; ++$i);
?>
<?php
for ($i = 0; $i < 10000000; $i++);
?>
sagacitydev@ch10106cus002 ~/junk $ time php -q pre.php ; time php -q
post.php
real 0m5.422s
user 0m5.350s
sys 0m0.070s
real 0m5.397s
user 0m5.330s
sys 0m0.070s
sagacitydev@ch10106cus002 ~/junk $ time php -q pre.php ; time php -q
post.php
real 0m5.164s
user 0m5.090s
sys 0m0.070s
real 0m5.310s
user 0m5.230s
sys 0m0.080s
sagacitydev@ch10106cus002 ~/junk $ time php -q pre.php ; time php -q
post.php
real 0m5.093s
user 0m5.030s
sys 0m0.070s
real 0m5.387s
user 0m5.300s
sys 0m0.080s
sagacitydev@ch10106cus002 ~/junk $ time php -q post.php ; time php -q
pre.php
real 0m5.429s
user 0m5.340s
sys 0m0.070s
real 0m5.140s
user 0m5.060s
sys 0m0.080s
sagacitydev@ch10106cus002 ~/junk $ time php -q post.php ; time php -q
pre.php
real 0m5.348s
user 0m5.270s
sys 0m0.070s
real 0m5.101s
user 0m5.030s
sys 0m0.070s
sagacitydev@ch10106cus002 ~/junk $ time php -q post.php ; time php -q
pre.php
real 0m5.376s
user 0m5.300s
sys 0m0.080s
real 0m5.009s
user 0m4.910s
sys 0m0.100s
sagacitydev@ch10106cus002 ~/junk $ php -v
PHP 4.4.7 (cli) (built: May 8 2007 09:49:19)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v1.3.0, Copyright (c) 1998-2004 Zend Technologies
sagacitydev@ch10106cus002 ~/junk $ uname -a
Linux ch10106cus002 2.6.18-hardened-r6 #2 SMP Tue Apr 17 09:15:05 CDT
2007 i686 Dual Core AMD Opteron(tm) Processor 270 AuthenticAMD
GNU/Linux
sagacitydev@ch10106cus002 ~/junk $
Perhaps the OP meant that not doing the count() / sizeof() on every
iteration was a 10% win? Now *THAT* I can believe!
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