From owner-freebsd-hackers@FreeBSD.ORG Tue Mar 14 08:15:17 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6FE1616A41F; Tue, 14 Mar 2006 08:15:17 +0000 (UTC) (envelope-from root@scienceclue.ath.cx) Received: from scienceclue.ath.cx (mic92-1-87-90-12-116.dsl.club-internet.fr [87.90.12.116]) by mx1.FreeBSD.org (Postfix) with ESMTP id C268443D49; Tue, 14 Mar 2006 08:15:14 +0000 (GMT) (envelope-from root@scienceclue.ath.cx) Received: from scienceclue.ath.cx (localhost [127.0.0.1]) by scienceclue.ath.cx (8.13.4/8.13.4) with ESMTP id k2E8GKVe055705; Tue, 14 Mar 2006 09:16:20 +0100 (CET) (envelope-from root@scienceclue.ath.cx) Received: (from root@localhost) by scienceclue.ath.cx (8.13.4/8.13.4/Submit) id k2E8GCPF055704; Tue, 14 Mar 2006 09:16:12 +0100 (CET) (envelope-from root) Date: Tue, 14 Mar 2006 09:16:12 +0100 From: Mathieu Prevot To: Dan Nelson Message-ID: <20060314081612.GA55608@scienceclue.ath.cx> References: <20060313161740.GA56875@scienceclue.ath.cx> <20060313171341.GA7636@dan.emsphone.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20060313171341.GA7636@dan.emsphone.com> User-Agent: Mutt/1.4.2.1i X-Operating-System: FreeBSD-AMD64 6.1-PRERELEASE X-URL: http://scienceclue.ath.cx X-Mailman-Approved-At: Tue, 14 Mar 2006 12:48:19 +0000 Cc: freebsd-hackers@freebsd.org, freebsd-amd64@freebsd.org Subject: Re: Creating real bool type for simulation in physics X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: Mathieu Prevot List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Mar 2006 08:15:17 -0000 On Mon, Mar 13, 2006 at 11:13:41AM -0600, Dan Nelson wrote: > In the last episode (Mar 13), Mathieu Prevot said: > > I use freebsd/amd64 (RELENG_6) for simulation in physics. I am > > working on the Ising model: an assembly of spins (micromagnets) which > > interact and which are in one of two states (up or down). Until now I > > use char to define the state of each spin (-1 or 1), however, I > > remarked that most time is spent on memory I/O. Most of bits are > > unused. > > > > I think that if I can use just one bit per spin, I can have something > > much faster. I need advices on how to use it. I guess I can't define > > a new type with a 1/8 byte height (or one bit), yes ? What variable > > (int, char...) do you recommend to use for a sempron 64 bits. I think > > I'll need to define new operators (opaque operators, built with bit > > operators) to switch my spins or use directly the following: & | ^ ~ > > ... > > Take a look at the "bitstring" functions, which let you allocate an > array of "bits" and manipulate them individually. They're documented > in the bitstring manpage. Thank you. bitstring functions (macros) are based on char (8bits) type. This is not ANSI or POSIX, I will include /usr/src/sys/sys/bitstring.h in my program for portability. vi (nvi), and bind9 also use these macros, but are a bit different. -- Mathieu P http://scienceclue.ath.cx