Author: Robert Hyatt
Date: 20:02:20 01/12/06
Go up one level in this thread
On January 11, 2006 at 19:13:11, Stuart Cracraft wrote: >On January 11, 2006 at 09:44:57, Robert Hyatt wrote: > >>On January 10, 2006 at 18:10:15, Stuart Cracraft wrote: >> >>>Here's Butler Lampson, one of the inventors, of the Parc Alto >>>talking about Seymour Cray and population-count units: >>> >>>http://research.microsoft.com/users/gbell/craytalk/sld051.htm >> >>Seymour said the same thing about the "leading zero" instruction, which was >>about the same thing as "find first one bit (starting from left) since the >>instruction just counting the leading zeros up to the first one. The Crypto >>folks used both. >> >>And yes, the 7600/Cyber-176 was a fast box in its day. Chess 4.x used it to >>drub other chess programs for a few of years until a certain program moved to >>even faster hardware (the Cray-1). :) > >Great stuff. > >Wish I had a population count instruction and find first one bit instruction! > >I hear that these exist on some chips but are not advertised. Intel has BSF/BSR which find first/last set one bit quickly. They work on X86-64 machines too so that they are available for full 64 bit operands, just like on a cray. But no popcnt. Apples have the leading zero type instruction as well. There are a few intrinsics used in Crafty to get to this if you search the source. I didn't write 'em however, someone contributed...
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.