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Date: Fri, 14 Oct 2011 23:39:18 +0400
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To: Arnaud Le Blanc <arnaud.lb@gmail.com>
CC: PHP Internals <internals@lists.php.net>, Andi Gutmans <andi@zend.com>,
	Zeev Suraski <Zeev@zend.com>, Stas Malyshev <smalyshev@sugarcrm.com>, Nikita
 Popov <nikita.ppv@googlemail.com>
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Subject: Re: Ternary operator performance improvements
From: dmitry@zend.com (Dmitry Stogov)

Hi,

As I already said, I don't see any technical issues with the patch.
I don't like it very mach, but it looks robust, and I don't object about it.

Thanks. Dmitry.

On 10/14/2011 10:08 PM, Arnaud Le Blanc wrote:
> Hi,
>
> I've already posted this patch and it has since been reviewed and improved.
> I'm re-posting it for discussion before eventually commiting it.
>
> The ternary operator always copies its second or third operand, which is very
> slow compared to an if/else when the operand is an array for example:
>
> $a = range(0,9);
>
> // this takes 0.3 seconds here:
>
> for ($i = 0; $i<  5000000; ++$i) {
>          if (true) {
>                  $b = $a;
>          } else {
>                  $b = $a;
>          }
> }
>
> // this takes 3.8 seconds:
>
> for ($i = 0; $i<  5000000; ++$i) {
>          $b = true ? $a : $a;
> }
>
> I've tried to reduce the performance hit by avoiding the copy when possible
> (patch attached).
>
> Benchmark:
>
> Without patch: (the numbers are the time taken to run the code a certain
> amount of times)
>
> $int = 0;
> $ary = array(1,2,3,4,5,6,7,8,9);
>
> true ? 1 : 0        0.124
> true ? 1+0 : 0      0.109
> true ? $ary : 0     2.020 !
> true ? $int : 0     0.103
> true ? ${'ary'} : 0 2.290 !
> true ?: 0           0.091
> 1+0 ?: 0            0.086
> $ary ?: 0           2.151 !
> ${'var'} ?: 0       2.317 !
>
> With patch:
>
> true ? 1 : 0        0.124
> true ? 1+0 : 0      0.195
> true ? $ary : 0     0.103
> true ? $int : 0     0.089
> true ? ${'ary'} : 0 0.103
> true ?: 0           0.086
> 1+0 ?: 0            0.159
> $cv ?: 0            0.090
> ${'var'} ?: 0       0.089
>
>
> The array copying overhead is eliminated. There is however a slowdown in some
> of the cases, but overall there is no completely unexpected performance hit as
> it is the case currently.
>
> What do you think ? Is there any objection ?
>
> Best regards,