220 37542 <20180328155102.5083219.89905.48476@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Remove floating point requirement for unordered (multi) set/map Date: Wed, 28 Mar 2018 11:51:02 -0400 Lines: 114 Approved: news@gmane.org Message-ID: <20180328155102.5083219.89905.48476@gmail.com> References: <4c98e549-8f0c-42e5-a054-0234f7cf1e46@isocpp.org> <9d4a8ea3-9e7d-4851-8b28-5cd67779081a@isocpp.org> <1356e140-2985-4fe7-b9ee-70e40738d1cf@isocpp.org> <7b853bcd-47f5-4c2c-841b-13e30472e14c@isocpp.org> <1df72d61-2659-4864-9a6d-f8ea8fe52792@isocpp.org> <8eb5c7cd-42ec-46bd-8aee-842ef11b885e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1522252142 22134 195.159.176.226 (28 Mar 2018 15:49:02 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 28 Mar 2018 15:49:02 +0000 (UTC) To: Alberto Barbati , ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCUZ5QWKNQIOP47O2UCRUBAQJVD7K@isocpp.org Wed Mar 28 17:48:58 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f71.google.com ([209.85.214.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f1DJp-0005cH-TI for gclcip-std-proposals@m.gmane.org; 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[70.50.121.47]) by smtp.gmail.com with ESMTPSA id 199-v6sm3195930itl.5.2018.03.28.08.51.02 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 28 Mar 2018 08:51:02 -0700 (PDT) X-Mailer: BlackBerry Email (10.3.3.2205) In-Reply-To: <8eb5c7cd-42ec-46bd-8aee-842ef11b885e@isocpp.org> X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=r3UGmNjX; spf=pass (google.com: domain of tvaneerd@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Spam-Checked-In-Group: std-proposals@isocpp.org X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:37542 Archived-At: =
He said 'likely'.

The question is whether= you can find an STL implementation that doesn't use floating point interna= lly.

Implementations _could_ use fixed point internal= ly, but will they?

Maybe they would. Or ma= ybe they already do. You should ask your implementation. 
In fact, ask them to add an extension to = unordered_map =E2=80=8Ethat takes a percent or ratio or something.  On= ce there is an implementation with the extension, it might be easier to con= vince the committee. 
Either way, I think you co= uld write a proposal and see what the committee thinks.
= =

= = =
Sent from my Bla= ckBerry portable Babbage Device
= = =
=
From: Alberto= Barbati
Sent: Wednesday, March 28, 2018 11:42 AM
To: ISO C++ Standard - Future Proposals
Reply To: std-proposals@isocpp.org
Subject: Re: [std-proposals] Re:= Remove floating point requirement for unordered (multi) set/map


Il giorno mercol= ed=C3=AC 28 marzo 2018 17:35:48 UTC+2, Ben Craig ha scritto:
Even if you add new int= erfaces to deal with the load factor, the internals are likely to still nee= d to use floating point math in order to continue supporting the old interf= aces.  Unless you are willing to write your own std::unordered_* conta= iners and replace the ones shipped with libstdc++ or libc++ with those, you= will probably be stuck with some amount of floating point math in the cont= ainers.

reserve does math on the load factor. = ; insert does comparisons with the load factor.

That is incorrect. The implementation is allowed to store and use= internally a fixed point representation of the max load factor and perform= math on such value. The only places in which floating point is actually ne= cessary are the interface functions max_load_factor() and load_factor().

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