Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:100473
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.128.194 as permitted sender)
MIME-Version: 1.0
Sender: morrison.levi@gmail.com
In-Reply-To: <1504883189.2374.26.camel@schlueters.de>
References: <CAEsg9X0mUWuLjGEPuWF6w7m-PNG1V_WHRa8TSvs5L0pz1kgJ+A@mail.gmail.com>
 <1504883189.2374.26.camel@schlueters.de>
Date: Fri, 8 Sep 2017 09:35:55 -0600
Message-ID: <CAFMT4NquGc4Nr9uuxQz30GyZ3Jc=0BNycFAn7692tAdtXm0-Aw@mail.gmail.com>
To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Cc: David Rodrigues <david.proweb@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] array_filter vs for/foreach usage cost
From: levim@php.net (Levi Morrison)

On Fri, Sep 8, 2017 at 9:06 AM, Johannes Schl=C3=BCter
<johannes@schlueters.de> wrote:
> Hi,
>
> On Do, 2017-09-07 at 15:13 -0300, David Rodrigues wrote:
>> I understand that array_filter() should costs more than for/foreach
>> because
>> it is a function call that call another function for each item, while
>> the
>> for/foreach is a language constructor that works on a way totally
>> different
>> and its optimized for this kind of job.
>
> The main cost in that is that array_filter has to create a copy of the
> array. An alternative is using an FilterIterator or generator or such
> which would make this a pipeline step. (with iterators there are
> multiple function calls, while the function descriptor is cached,
> making them relatively cheap) I'd focus on improving those.

As far as I can tell from the source `array_filter` does not create a
copy of the array. It initializes a new array and then appends to it.

If we want to improve the performance of `array_filter` we need to
examine output of common compilers to see if they hoist the
have_callback check out of the loop; I suspect it may not given the
complexity of ZEND_HASH_FOREACH_KEY_VAL_IND.