Author: Robert Hyatt
Date: 19:58:32 12/21/99
Go up one level in this thread
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. 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.
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