220 37538 <8eb5c7cd-42ec-46bd-8aee-842ef11b885e@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Alberto Barbati Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Remove floating point requirement for unordered (multi) set/map Date: Wed, 28 Mar 2018 08:42:24 -0700 (PDT) Lines: 85 Approved: news@gmane.org Message-ID: <8eb5c7cd-42ec-46bd-8aee-842ef11b885e@isocpp.org> 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> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_23062_1254661168.1522251744654" X-Trace: blaine.gmane.org 1522251623 16304 195.159.176.226 (28 Mar 2018 15:40:23 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 28 Mar 2018 15:40:23 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCPY5DV6RIMBBYPP53KQKGQE2ONIXLQ@isocpp.org Wed Mar 28 17:40:19 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f200.google.com ([209.85.217.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1f1DBT-00049t-25 for gclcip-std-proposals@m.gmane.org; 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Wed, 28 Mar 2018 08:42:26 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.31.16.193 with SMTP id 62ls2391765vkq.16.gmail; Wed, 28 Mar 2018 08:42:25 -0700 (PDT) X-Received: by 10.31.148.135 with SMTP id w129mr2143344vkd.14.1522251745078; Wed, 28 Mar 2018 08:42:25 -0700 (PDT) In-Reply-To: <1df72d61-2659-4864-9a6d-f8ea8fe52792@isocpp.org> X-Original-Sender: AlbertoBarbati@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:37538 Archived-At: ------=_Part_23062_1254661168.1522251744654 Content-Type: multipart/alternative; boundary="----=_Part_23063_1456266454.1522251744654" ------=_Part_23063_1456266454.1522251744654 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Il giorno mercoled=C3=AC 28 marzo 2018 17:35:48 UTC+2, Ben Craig ha scritto= : > > Even if you add new interfaces to deal with the load factor, the internal= s=20 > are likely to still need to use floating point math in order to continue= =20 > supporting the old interfaces. Unless you are willing to write your own= =20 > std::unordered_* containers and replace the ones shipped with libstdc++ o= r=20 > libc++ with those, you will probably be stuck with some amount of floatin= g=20 > point math in the containers. > > reserve does math on the load factor. insert does comparisons with the= =20 > load factor. > That is incorrect. The implementation is allowed to store and use=20 internally a fixed point representation of the max load factor and perform= =20 math on such value. The only places in which floating point is actually=20 necessary are the interface functions max_load_factor() and load_factor(). --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/8eb5c7cd-42ec-46bd-8aee-842ef11b885e%40isocpp.or= g. ------=_Part_23063_1456266454.1522251744654 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

Il giorno mercoled=C3=AC 28 marzo 2018 17:35:48 UTC+2,= Ben Craig ha scritto:
Even if you add new interfaces to deal with the load factor, = the internals are likely to still need to use floating point math in order = to continue supporting the old interfaces.=C2=A0 Unless you are willing to = write your own std::unordered_* containers and replace the ones shipped wit= h libstdc++ or libc++ with those, you will probably be stuck with some amou= nt of floating point math in the containers.

reser= ve does math on the load factor.=C2=A0 insert does comparisons with the loa= d factor.

That is incorrect. The imple= mentation is allowed to store and use internally a fixed point representati= on of the max load factor and perform math on such value. The only places i= n which floating point is actually necessary are the interface functions ma= x_load_factor() and load_factor().

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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/8eb5c7cd-42ec-46bd-8aee-842ef11b885e= %40isocpp.org.
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