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Date: Mon, 17 Oct 2011 08:52:21 -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>, Dmitry Stogov <dmitry@zend.com>, 
	Nikita Popov <nikita.ppv@googlemail.com>
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Subject: Re: [PHP-DEV] Ternary operator performance improvements
From: ilia@prohost.org (Ilia Alshanetsky)

Seems like a good patch, +1 from me on inclusion into 5.4/HEAD.

On Fri, Oct 14, 2011 at 2:08 PM, Arnaud Le Blanc <arnaud.lb@gmail.com> wrot=
e:
> Hi,
>
> I've already posted this patch and it has since been reviewed and improve=
d.
> 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:
>
> $a =3D range(0,9);
>
> // this takes 0.3 seconds here:
>
> for ($i =3D 0; $i < 5000000; ++$i) {
> =A0 =A0 =A0 =A0if (true) {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$b =3D $a;
> =A0 =A0 =A0 =A0} else {
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0$b =3D $a;
> =A0 =A0 =A0 =A0}
> }
>
> // this takes 3.8 seconds:
>
> for ($i =3D 0; $i < 5000000; ++$i) {
> =A0 =A0 =A0 =A0$b =3D true ? $a : $a;
> }
>
> I've tried to reduce the performance hit by avoiding the copy when possib=
le
> (patch attached).
>
> Benchmark:
>
> Without patch: (the numbers are the time taken to run the code a certain
> amount of times)
>
> $int =3D 0;
> $ary =3D array(1,2,3,4,5,6,7,8,9);
>
> true ? 1 : 0 =A0 =A0 =A0 =A00.124
> true ? 1+0 : 0 =A0 =A0 =A00.109
> true ? $ary : 0 =A0 =A0 2.020 !
> true ? $int : 0 =A0 =A0 0.103
> true ? ${'ary'} : 0 2.290 !
> true ?: 0 =A0 =A0 =A0 =A0 =A0 0.091
> 1+0 ?: 0 =A0 =A0 =A0 =A0 =A0 =A00.086
> $ary ?: 0 =A0 =A0 =A0 =A0 =A0 2.151 !
> ${'var'} ?: 0 =A0 =A0 =A0 2.317 !
>
> With patch:
>
> true ? 1 : 0 =A0 =A0 =A0 =A00.124
> true ? 1+0 : 0 =A0 =A0 =A00.195
> true ? $ary : 0 =A0 =A0 0.103
> true ? $int : 0 =A0 =A0 0.089
> true ? ${'ary'} : 0 0.103
> true ?: 0 =A0 =A0 =A0 =A0 =A0 0.086
> 1+0 ?: 0 =A0 =A0 =A0 =A0 =A0 =A00.159
> $cv ?: 0 =A0 =A0 =A0 =A0 =A0 =A00.090
> ${'var'} ?: 0 =A0 =A0 =A0 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 h=
it as
> it is the case currently.
>
> What do you think ? Is there any objection ?
>
> Best regards,
>
> --
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