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 _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
