Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:123826
Date: Tue, 25 Jun 2024 17:12:44 +0100
To: "Saki Takamachi" <saki@sakiot.com>
Cc: "php internals" <internals@lists.php.net>
Message-ID: <190502bc4bf.1145fe1df199171.9215746182322416249@barneylaurance.uk>
In-Reply-To: <90AAEBAA-30DC-40B4-AEBD-D4958753324A@sakiot.com>
References: <90AAEBAA-30DC-40B4-AEBD-D4958753324A@sakiot.com>
Subject: Re: [PHP-DEV] Add bcdivmod() to BCMath
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Importance: Medium
User-Agent: Zoho Mail
From: barney@barneylaurance.uk (Barney Laurance)


 ---- On Tue, 25 Jun 2024 10:11:10 +0100  Saki Takamachi  wrote --- 
 > Hi internals,
 > 
 > I've been working on improving performance of BCMath lately, and I found that I can get the div and mod in one calculation. This is obviously faster than calculating it twice separately.
 > 
 > Do you think there's a demand for this feature?
 > 
 > e.g.
 > ```
 > [$quot, $rem] = bcdivmod('123', '2');
 > // $quot is '61', $rem is '1'
 > ```
 > 
 > The naming and return value scheme is inspired by Python and Ruby.
 > 
 > Of course, if this is added, equivalent functionality will be added to the Number class.

I'm wondering whether this needs to be a change to the API, or if it might be better implemented as a purely internal optimisation to BCMath / Number - in some way memoize both the quotient and the remainder when either div or mod is called, and then document for users that calling one after the other will be extremely cheap to run.

But maybe that brings up too many questions about memory usage - e.g. is the memory for this reserved in advance for each instance of Number, or allocated when one of these functions is called, and should it be freed even while the object remains in scope to avoid using lots of memory if many numbers are divided or modded.