Author: Robert Hyatt
Date: 06:47:10 12/22/99
Go up one level in this thread
On December 22, 1999 at 04:34:43, Ed Schröder wrote: >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 > > You are correct. It was a bishop for a pawn, not a whole bishop. My error... Bob I believe _their_ score was +2.6 or so in reality, as I think they used 128 for a pawn back then. >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.