From -8835041625125781364 X-Google-Thread: f78e5,27c2a088314ec0a9 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news4.google.com!news.glorb.com!news2.telebyte.nl!border2.nntp.ams.giganews.com!border1.nntp.ams.giganews.com!nntp.giganews.com!news-hub.cableinet.net!blueyonder!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: dhruvbird@gmx.net ("Dhruv Matani") Newsgroups: comp.std.c++ Subject: Re: should std::vector<> exponential growth rate be followed strictly in times of low availabe memory. Date: Fri, 5 Nov 2004 06:18:04 GMT Lines: 52 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: References: <417E434E.5000209@bubblescope.net> <4fvjo0t07isfber4rblifh56jmiq2glrnj@4ax.com> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: news.demon.co.uk 1099635494 25439 158.152.254.254 (5 Nov 2004 06:18:14 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Fri, 5 Nov 2004 06:18:14 +0000 (UTC) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Pan/0.13.3 (That cat's something I can't explain) X-Orig-X-Trace: news.uni-berlin.de oAaHzw+KLfyWiAOs8yS5lwHibMpNiUwTxK1m+FZBzdCIR2P3Ql X-Virus-Scanned: by amavisd-new at cs.mu.OZ.AU X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id iA56I4rM004265; Fri, 5 Nov 2004 17:18:04 +1100 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-Delivered-To: std-c++@ucar.edu X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ Xref: g2news1.google.com comp.std.c++:3289 On Thu, 04 Nov 2004 22:29:30 +0000, Tom Widmer wrote: > On Wed, 27 Oct 2004 03:43:46 GMT, dhruvbird@gmx.net ("Dhruv Matani") > wrote: > >>Yes, but it would obviously be a nonsense implementation as you have >>mentioned. I'm looking more at making it allowable by the standard in >>such low memory situations to deviate from the exponential growth >>policy. > > And the standard already allows that, since it doesn't specify > "exponential growth", but rather amortized constant time push_back. > > However, I don't think a 1GB+ std::vector is a very good idea in any > case. If you use malloc, then you get access to realloc, or you should > perhaps be using a custom allocator, or redesigning your algorithm, > perhaps to allow a segmented container of some kind, or to use less > RAM. Yes, but in certain cases, it becomes necessary for using such big vectors. Like in my case, I want to use it as a replacement for std::multimap<>, because: 1. The locality of the nodes is destroyed by the re-balancing algorithm, and 2. Every insertion involves touching a lot of data, so places where data is coming in at a very fast rate, this is unacceptable. So, I would rather use a vector and then sort it after all the insertions are over.(because the application/use happens to be ammenable to that change). Here, I know in advance the maximum size of the vector, but in other cases I might not. Now, given that fact that I have say 2GB of Phy. mem. I should not be consrtained by the exponential growth policy. Also, as others have mentioned, the underlying implementation could use 1.5 as the factor, but then, again that would cause a lot of copies unnecessarily. Esp. for a heavy copying object. But, then again looking at Dave Harris' reply, I'm not quite convinced about the way I'm using vector? Maybe? Reards, -Dhruv. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]