Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:85778
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.217.177 as permitted sender)
Message-ID: <552B936E.1070804@gmail.com>
Date: Mon, 13 Apr 2015 10:59:10 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0
MIME-Version: 1.0
To: internals@lists.php.net
References: <2FECEA44-6299-4984-8789-C0A107D88C4B@gmail.com> <552B36C7.7080102@gmail.com>
In-Reply-To: <552B36C7.7080102@gmail.com>
Content-Type: multipart/alternative;
 boundary="------------010309050106070605000209"
Subject: Re: [PHP-DEV] $max > getmaxrand() for rand() call
From: rowan.collins@gmail.com (Rowan Collins)

--------------010309050106070605000209
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit

Stanislav Malyshev wrote on 13/04/2015 04:23:
>> <https://bugs.php.net/bug.php?id=69396>) - to sum up: if you provide
>> $max parameter that is larger than OS-provided getmaxrand(), the
>> result will be artificially stretched, which in result leads to some
>> values not appearing at all. That’s troublesome if for instance some
>> people use that function to choose random server for a service, and
>> the stretched result wouldn’t return even values at all.
> How many servers you've got? Also, why not use mt_rand()? It has max of
> 2^^31, if you have more servers than that you probably have very
> uncommon use case :)

To be fair, that's not actually mutually exclusive with Leszek's 
suggestions - we still need to either document, or warn, that rand() has 
this limitation. The manual does actually mention using mt_rand(), but 
also suggests setting $max higher than getrandmax(), which is probably 
bad advice:

 > If you require a range larger than 32767, specifying |min| and |max| 
will allow you to create a range larger than this, or consider using 
mt_rand() <http://php.net/manual/en/function.mt-rand.php> instead.

Regards,
-- 
Rowan Collins
[IMSoP]

--------------010309050106070605000209--