Author: Robert Hyatt
Date: 13:10:54 11/19/02
Go up one level in this thread
On November 19, 2002 at 15:05:29, Vincent Diepeveen wrote: >On November 19, 2002 at 14:14:35, Robert Hyatt wrote: > >If you want to keep your thing at kindergarten level, >bitboards is the way to go of course :) Remember how you do when you play this "kindergarten level" program... > >>On November 19, 2002 at 13:30:57, Christophe Theron wrote: >> >>>On November 19, 2002 at 13:15:09, Gerd Isenberg wrote: >>> >>>>On November 19, 2002 at 12:25:11, Gian-Carlo Pascutto wrote: >>>> >>>>>On November 19, 2002 at 11:35:24, Robert Hyatt wrote: >>>>> >>>>>>Bitboards have a bit of a performance advantage on 64 bit processors, >>>>> >>>>>Proof? >>>>> >>>>>-- >>>>>GCP >>>> >>>>Hi Gian-Carlo, >>>> >>>>I think that's evident. If the none bitboarders have to use implicite native >>>>data-width of 64 bit integers, they have to transfer 32 additional zero bits >>>>without any additional information for each integer access. Of course you will >>>>pack some data, but all the local ints... >>>> >>>>So the information density for bitboarders grows with 64bit-architectures >>>>relative to none bitboarders. That also effects register usage, and that's IMHO >>>>more important. On x86-32bit architectures you can only hold three bitboards in >>>>registers, and thats even most a hard task. Actually, if you have a local >>>>routine with three bitboards and a few ints on the stack, there are a lot >>>>register/memory moves. Simply the data-width doubles the number of bitboard >>>>registers, not considered the increase in general purpose registers, or with >>>>hammer the number of mmx- and 128-bit xmm registers. >>>> >>>>Whether a bitboard based program is stronger than a none bitboard program >>>>depends obviuosly also on other things, but in principle :) >>>> >>>>Cheers, >>>>Gerd >>> >>> >>> >>>You have just explained why the bitboarders are less handicapped on 64 bits >>>machines. >>> >>>You have not explained why they are supposed to have "a bit of performance >>>advantage on 64 bits processors". >>> >>> >>> >>> Christophe >> >> >>Actually he _did_ explain. A 32 bit program, running on a 64 bit machine, >>simply passes >>32 bit values around, taking _no_ advantage from the additional 32 bits of data >>that is >>available. A bitboard program, on the other hand, _does_ get an advantage. >>Rather than >>having to use two instructions for 64 bit AND/OR/XOR instructions, it can use >>just one. >>Rather than using even more to do 64 bit shifts, it uses just one. >> >>Seems intuitive that 64 bit programs will run faster on a 64 bit processor, even >>if the 64 bit >>processor executes instructions _exactly_ at the same speed (and using the same >>number of >>registers and so forth). All the 64 bit stuff reduces to a single instruction, >>while the normal >>chess program does _exactly_ the same work on either...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.