220 34892 <1550fc17-cf97-438d-9e7a-862f729adbf5@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Todd Fleming Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Thoughts on more methods towards containers in the future Date: Sat, 14 Oct 2017 06:18:56 -0700 (PDT) Lines: 99 Approved: news@gmane.org Message-ID: <1550fc17-cf97-438d-9e7a-862f729adbf5@isocpp.org> References: <973f04da-1354-44f4-9d1f-23f04596b8dc@isocpp.org> <20171014085305.GA24512@fukushima.lysator.liu.se> <79c51b8c-6cc2-4872-8651-9dae513d1e21@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_14316_93442328.1507987136473" X-Trace: blaine.gmane.org 1507987142 20289 195.159.176.226 (14 Oct 2017 13:19:02 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 14 Oct 2017 13:19:02 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDN5JUVZSIFBBQM5RDHQKGQETKNPDOY@isocpp.org Sat Oct 14 15:18:58 2017 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 1e3ML4-0003hm-Qx for gclcip-std-proposals@m.gmane.org; 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Sat, 14 Oct 2017 06:18:58 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.176.2.9 with SMTP id 9ls2388185uas.19.gmail; Sat, 14 Oct 2017 06:18:56 -0700 (PDT) X-Received: by 10.31.11.69 with SMTP id 66mr285966vkl.6.1507987136952; Sat, 14 Oct 2017 06:18:56 -0700 (PDT) In-Reply-To: <79c51b8c-6cc2-4872-8651-9dae513d1e21@isocpp.org> X-Original-Sender: tbfleming@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: 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:34892 Archived-At: ------=_Part_14316_93442328.1507987136473 Content-Type: multipart/alternative; boundary="----=_Part_14317_361490490.1507987136473" ------=_Part_14317_361490490.1507987136473 Content-Type: text/plain; charset="UTF-8" On Saturday, October 14, 2017 at 8:45:29 AM UTC-4, ejsvifq mabmip wrote: > > On Saturday, October 14, 2017 at 4:53:10 AM UTC-4, Magnus Fromreide wrote: >> >> On Fri, Oct 13, 2017 at 07:38:20PM -0700, eulo...@live.com wrote: >> > Contiguous Containers: >> > >> > vector: >> > add non check push_back. non check resize etc. >> >> What does this mean, you are a bit thin on details here. >> >> ok. when you push_back an element into the vector, it will first check > whether size()==capacity(). It is an overhead when you know what exactly > the size of elements you need. > > For example: > > vector v; > v.reserve(10000000); > for(std::size_t i(0);I!=v.capacity();++i) > v.emplace_back(i); > > will be slower than > > vector v; > v.reserve(10000000); > for(std::size_t i(0);I!=v.capacity();++i) > v.nonchecked_emplace_back(i); > Benchmark requested using -O2 or higher; I doubt your performance claim. Todd -- 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 email 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/1550fc17-cf97-438d-9e7a-862f729adbf5%40isocpp.org. ------=_Part_14317_361490490.1507987136473 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Saturday, October 14, 2017 at 8:45:29 AM UTC-4, ejsvifq= mabmip wrote:
On Saturday, October 14, 2017 at 4:53:10 AM UTC-4, Magnus Fromreide wrote:=
On Fri, Oct 13, 2017 at 07:38:20PM = -0700, eulo...@live.com wrote:
> Contiguous Containers:
>=20
> vector:
> add non check push_back. non check resize etc.

What does this mean, you are a bit thin on details here.

ok. when you push_back an element into the vector, it= will first check whether size()=3D=3Dcapacity(). It is an overhead when yo= u know what exactly the size of elements you need.

For example:

vector<std::size_t> v;
v.reserve(10000000);
for(std::size_t i(0);I!=3Dv.capacity(= );++i)
=C2=A0 =C2=A0=C2=A0 v.emplace_back(i);

will be slower than

vector<std::size= _t> v;
v.reserve(10000000);
for(std::= size_t i(0);I!=3Dv.capacity();++i)
=C2=A0 =C2=A0=C2=A0 v.noncheck= ed_emplace_back(i);

Bench= mark requested using -O2 or higher; I doubt your performance claim.

Todd

--
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