Author: Ed Schröder
Date: 01:34:43 12/22/99
Go up one level in this thread
On December 21, 1999 at 22:58:32, Robert Hyatt wrote: >On December 21, 1999 at 18:31:58, Vincent Diepeveen wrote: > >>On December 21, 1999 at 17:44:06, Robert Hyatt wrote: >> >>>On December 21, 1999 at 17:02:53, Greg Lindahl wrote: >>> >>>>On December 21, 1999 at 16:18:27, Albert Silver wrote: >>>> >>>>>That's correct, he says it was done through software: "During the 1997 match, >>>>>the software search extended the search to about 40 plies along the forcing >>>>>lines, even though the nonextended search reached only about 12 plies." He also >>>>>mentions that "The software portion of the search can be arbitrarily selective >>>>>without slowing down the system." >>>> >>>>If you read the beginning of that paragraph, Hsu explicitly says that the 8 >>>>plies of software search included forcing. Hsu doesn't say if the final 4 plies >>>>of hardware search included forcing by droping back to software or not. Given >>>>that the chess chips seem to operate in an embarrassingly parallel fashion, I >>>>would suspect that there was no forcing for those plies. Someone could always >>>>ask Hsu... >>>> >>> >>> >>> >>>Old news. The first 4 plies (+ whatever extensions were used) were done on a >>>single SP processor. The next 4 plies + whatever extensions were triggered were >>>done in parallel on the SP, which (if stated simply) says that the first 8 >>>plies, plus all the extensions, are done on the general-purpose SP hardware. >>>The _final_ 4 plies, plus the capture search were done on the chess processors. >>>The chess processors _did_ do extensions, but not singular extensions. IE Ken >>>Thompson did the usual in-check and recapture extensions in Belle, and the >>>first deep thought (chiptest) chip was nothing more than "belle on a chip". >>> >>>Also, chess is _far_ from "embarassingly parallel". It is one of the more >>>difficult-to-program parallel algorithms, because alpha/beta is a strictly >>>defined sequential algorithm. Doing it in parallel invites a lot of extra >>>work that can't be avoided. >> >>I couldn't say it better Bob! >> >>>>How important is forcing in shallow plies verses deeper plies? That's easy to >>>>examine using a program. >>>> >>>>-- greg >>> >>> >>>Hsu would _like_ to have been able to do singular extensions in hardware. But >>>there was simply not enough space on the chip as things get _very_ complex >>>compared to a simple alpha/beta hardware design... >>> >>>But you have to ignore some of Vincent's ramblings about DB's search depth. I >>>once posted a position where they found a forced win of material OTB vs Cray >>>Blitz, as but one example of their extreme tactical strength. _NOBODY_ found >>>that win OTB, or overnight. Many liked the move, but _nobody_ saw the tactical >>>consequences that were forced. They have done this _many_ times over the >>>years. So I'd say their "11-ply search" is _far_ better than our 14-15 ply >>>searches, no questions asked... >> >>Bob, i explained that the c5 move was because of a horizon effect in deep blue. >>Diep had the same horizon effect too when i added the extension. > >No, you explained _your_ programs failing there. I _saw_ their PV and eval. >It was +3. Not +1.1 or something like that. Last time you said +2 remember? Ed It saw the bishop being taken >in the PV output. Remember that I was sitting there, talking with Murray and >Hsu during the game, when they failed high. Murray commented "DT seems to want >to pick on your bishop, but I don't see why that would fail high unless there is >a trick I don't see." A bit later (less than a minute) Murray said "Hey, it >is winning your bishop outright..." Our score was still good. It remained >good for at least another 5 moves before it started to drop. And by the time >10 moves had passed we were at -3. > >But they saw it from the _beginning_. > > > > > > >> >>Secondly an optimistic evaluation function or a program doing the Rxa4 >>in the quiescencesearch is gonna find things a lot faster than a smart >>qsearch that is not doing Rxa4 in the qsearch. >> >>Before this gets a blindfolded discussion, first here the position: >> >>black timeleft=27:46.40.00 >> r = - = - b k = Qa7-e3 20 Rf8-a8 >> = - = - = r o o c2-c3 21 Qb4-b7 >> - B o o b o - = Rf1-f2 22 Qb7-a7 >> = - = - n - = - Qe3xa7 23 Ra8xa7 >> N = - = - = - = Bf4-e3 24 Ra7-a5 >> = O O - = - = - Be3-b6 25 Ra5-a8 >> O = B = - R O O Bd3-c2 26 Be7-f8 >> = - = - R - K - Rd1-e1 27 ... >>white timeleft=27:46.40.00 >>black to move >> >>Note that it's smarter to get the last few moves for repetitions, >>that speeds up the search proces *considerable*, as last few moves >>were not exactly the most exciting moves. >> >>r4bk1/5rpp/1Bppbp2/4n3/N7/1PP5/P1B2RPP/4R1K1 b - - >> >>the main idea in this position is that after c5 the bishop on b6 is more >>or less hung. Now this doesn't mean that black sees the forced win, >>because seeing a forced win here means +5.0. >> > >I count a bishop as 3. Their eval was over +3. They _saw_ it. > > > > >>What is the problem here? Well the big problem for nowadays smart programs >>is that after a couple of moves there goes a rook to b7 and >>white for some reasons must move a rook to b-file. all bishops are >>gone then from their places which allows Rxa4 bxa4 Rxb1 in quiescencesearch. >>However not all programs play Rxa4 in qsearch. >> >>Just get away the c2 bishop and the b6 bishop and put the white rook to >>b2 and the black rook to b7. Not many programs will play Rxa4 here in >>quiescencesearch, as that's covered by a pawn, meaning an exchange gets >>lost. >> >>The score of Deep Blue here is however based upon a horizon effect which >>i posted a couple of time ago. This doesn't take away that *all* programs >>will play c5 here with a good score for black. Nowadays DIEP is very >>optimistic in such endgames too. Let's see whether i can get the same >>high score with the normal version of DIEP here searching fullwidth... > >I certainly can't get it with Crafty. And I didn't get it with Cray Blitz. >No one else that tried this last year got it either... although several got >the right move, but way wrong eval/PV.
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.