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Date: Sat, 4 May 2013 22:28:09 +0800
Message-ID: <CABBJUpdWS_y3z9jdHD2_5_tW9dZb29HFQjuNuotH6Eir9iUE5A@mail.gmail.com>
To: Anthony Ferrara <ircmaxell@gmail.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e0160b9d206131f04dbe54894
Subject: Re: [PHP-DEV] Re: [PROPOSAL]Add second to callback of preg_replace_callback
From: laruence@php.net (Laruence)

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On Sat, May 4, 2013 at 9:46 PM, Anthony Ferrara <ircmaxell@gmail.com> wrote:

> Laruence,
>
> > foreach ($replacements as $regex => $callback) {
> > >     $str = preg_replace_callback($regex, $callback, $str);
> > > }
> > >
> >
> >  So if there are 10 regex in the array, you will got 10 DO_FCALL. 10
> times
> > arguments accept, 10 times etc...
> >
> >  and AS I already said: IT is inefficient. I personally can not accept
> it.
> >
> > thanks
> >
> >
> My initial reaction was that the difference in runtime is going to be so
> insignificant that it's the very definition of a micro-optimization between
> the two. And unless you're doing it millions of times in a hot-loop, it's
> never even going to be realized. I was going to reply to that effect.
>
> Then I decided to write a quick test.
>
> $count = 100;
>
> $start = microtime(true);
> for ($i = 0; $i < $count; $i++) {
>     $str = "abc";
>     $str = preg_replace_callback('/a/', function($a) { return
> strtoupper($a[0]); }, $str);
>   $str = preg_replace_callback('/b/', function($a) { return
> strtoupper($a[0]); }, $str);
>     $str = preg_replace_callback('/c/', function($a) { return
> strtoupper($a[0]); }, $str);
>     $str = preg_replace_callback('/a/', function($a) { return
> strtolower($a[0]); }, $str);
>     $str = preg_replace_callback('/b/', function($a) { return
> strtolower($a[0]); }, $str);
>     $str = preg_replace_callback('/c/', function($a) { return
> strtolower($a[0]); }, $str);
> }
> echo "Completed in " . (microtime(true) - $start) . " Seconds\n";
>
> $start = microtime(true);
> for ($i = 0; $i < $count; $i++) {
>     $str = "abc";
>     $str = preg_replace(array(
>           '/a/e',
>             '/b/e',
>             '/c/e',
>             '/a/e',
>             '/b/e',
>             '/c/e',
>         ),
>         array(
>             'strtoupper(\'$1\')',
>             'strtoupper(\'$1\')',
>             'strtoupper(\'$1\')',
>             'strtolower(\'$1\')',
>             'strtolower(\'$1\')',
>             'strtolower(\'$1\')',
>         ),
>         $str
>     );
> }
> echo "Completed in " . (microtime(true) - $start) . " Seconds\n";
>
> So basically, it's comparing the old behavior (one call to preg_replace)
> that you want to emulate, with what Nikita is suggesting.
>
> I ran it on 3v4l (http://3v4l.org/dRjtU) and the results were quite
> surprising. I was expecting the first to be slightly slower than the
> second. But the reality surprised me:
>
> Completed in 0.00076389312744141 Seconds Completed in 0.0012428760528564
> Seconds
>
> As it turns out, calling preg_replace_callback() multiple times is almost
> 50% faster than using a single call to preg_replace().
>
> It's likely due to the precompiled nature of closures, vs the compilation
> happening multiple times at invocation in the preg_replace /e case.
>
> But it's still worth noting that switching from the /e style to a more
> traditional preg_replace_callback implementation will get you a significant
> boost in performance of that.
>
> Now, keep in mind, we're talking 0.000005 seconds saved per "execution"
> (group of 6 replacements). So it's not likely to matter much or be worth
> worrying about...
>
Hey:
  thanks for the benchmark, but please don't think it's useless just
because it's monior

  PHP is a web program language, let's think about a high trafiic site,
which get 100, 000, 000 pv perday.

  100, 000, 000 * 0.0000005 = 500s perday

  and inefficent not always means performance only,  in this case , you
need to define various functions for different regexs if you use loop style.

  and do you prefer array_walk or foreach when you try to iteraterly
process an array?


thanks

>
> My $0.02 at least...
>
> Anthony
>



-- 
Laruence  Xinchen Hui
http://www.laruence.com/

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