Author: Jeremiah Penery
Date: 09:42:51 01/17/00
Go up one level in this thread
On January 17, 2000 at 11:13:44, Vincent Diepeveen wrote: >On January 17, 2000 at 09:32:40, Robert Hyatt wrote: > >>On January 17, 2000 at 03:11:34, Jouni Uski wrote: >> >>>Yes stunnigly they are available at: >>> >>>http://www.research.ibm.com/deepblue/watch/html/c.html >>> >>>First thing I notice is, that search depth is not very convincing at all - >>>mostly 11-12 ply (also in endgame part)! Have I read log wrong way? Most >>>Chessbase engines got same ply in standard PC... >>> >>>Jouni >> >> >>It is a "different" kind of ply. DB didn't use null-move of any kind. They > >You can also search a lot less deeply without alfabeta pruning. >Even with an incredible amount of nodes you hardly will come deeper than >a few plies then. This means nothing. Null-move and other types of forward pruning or selective search can cause you to miss things. Hsu didn't want DB missing anything this way. (And don't tell me there is _no_ position where Diep fails because of a nullmove, or some other pruning, problem.) >>also used singular extensions which cause the typical chess ram to search >>1-2 plies less deep in the typical case, although it will probe much deeper > >Nah, singular extensions were introduced when chiptest searched up to 8 ply >at tournament level. From experiences at ICC server i can ASSURE everyone >that 8 ply is not enough to see even some simple tactical tricks. What are you talking about? In the same program with SE vs. without SE, the version with SE will search a ply or two less in iteration depth, but it will search deeper in critical lines. This is exactly what Bob just said. I have no idea what you're talking about here... >SURE singular extensions gave a lot back then, as no one got to 8 ply then, >so everyone was suffering from major tactical problems. > >Those get away when slowly getting above 10 ply, which is near to 6 moves >with some extensions, as was already estimated by De Groot back in 1966, >as being the 'basic plan depth of a master'. > >Later when they had deep thought II, getting 10 ply with an incredible >number of nodes a second, then the deep thought team themselves CLAIMED >that singular extensions didn't give much anymore. Let me quote: > >"the main conclusion that must be drawn from the experiments onse lective search >reported in this article is that while selective search, in particular >domain-independant selective search, does indeed improve the performance of a >chessprogram, no single heuristic is able to contribute a large improvement. >Moreover, many heuristics or variations that might appear promising in >theory turn out to be of little or no value in practics". That's not saying anything about SE. That paragraph is talking about null-move and other pruning methods (Hint: it uses the words "selective search". SE is not selective search.) >I can support to some extend this opinion. Nearly everything a human >does is extremely knowledge based. I'm never gonna look at a certain >forced line if my brain doesn't feel like wnating to look like it. >alfa nor beta have to do with this (as far as you can as human be aware >of any values, i'm not). > >Then conclusion goes on: > >"the total improvement of the best combination of heuristics discovered >so far over brute force is 72 points (86 USCF). Of this 49 points is >due to threat extensions, 7 points is due to singular extensions, 5 >points due toe PV lookahead extensions, with the reaminder due to a number of >less important extensions". > >I could not assigne values to the worth of extensions, >and I'm missing recapture extensions btw. Note that i could never proof them >working in tournament games either, but in blitz they kick butt, just >like mating extensions. > >I agree however with the conclusion. Everything a human does is knowledge >based. If we use a bit of knowledge, either dynamic or static, then >this means that search is gonna miss a lot. obviously you need something >to see deep threats/checks a bit deeper, to not lose all games because >of a mate in 7. > >However, i feel only evaluation is important. My current version of >DIEP is tactical simply weak. However if i turn back on all extensions it >used to have, then it's gonna score like 300 points at least more at >a given testset than the current version (the current version does it really >weak on those testsets, only win at chess gets still solved with 299 out >of 300, which btw is bigtime better than chiptest with 500k nps did, though >evaluation based). What were Chiptest's results? >I feel however that at slow level (where diep gets >= 10 ply) >score of diep is not gonna be different a lot. How much difference >is at blitz we'll see within some weeks/months at the icc server against >other programs and against humans. > >>in the traditional sense. One other unknown is whether their 10 plies includes >>the 4 plies of hardware search. They don't count total nodes that I noticed > >If they print '11' then they did get 11 ply brute force, which INCLUDES >the chessprocessors. No it doesn't. Because when they print '3', it obviously cannot include the 4 extra from the chess-processors. Note that the PVs they give also don't include stuff from the chess-processors. >It's impossible to get fullwidth without hashtables at chessprocessors, >with the way parallellism was set up, >and without the chessprocessors communicating hash etcetera with each >other to get 15 ply fullwidth, WITH a load of extensions. How do you assume they could communicate with each other? IIRC, there was no shared hash table among the chess-processors. It was a message passing setup, which would make what you're saying WAY too slow. >Note that Hsu describes that a typical 12 ply search was first 4 ply >at processor 1, then 4 ply at 30 different processors, then 4 ply in hardware. But I don't think that's the way it was shown in the log. >>anywhere, so it isn't easy to decide. For me, 1M nodes per second gives a >>depth of 13-14 in the middlegame. Going 200M should drive that to roughly >>log3(200) which is about 5 plies deeper. So call that 18-19 plies. Removing >>null-move would subtract 2, so 16-17 plies. Singular extensions 1-2 more plies, >>so that would be (14-15) to (15-16) plies. >>Somewhere on their web site they mentioned 14 plies as "normal". So their >>iteration number might be slightly different from "ours". IE when I search >>until depth is reduced to zero, I go to the quiescence search. They might >>go to their hardware, which is not exactly a "quiescence search" since it looks >>at all moves for 4 plies, but doesn't do any of the singular stuff and so forth. >>I'll try to ask next time I hear something from Hsu. > >He implicitly answerred that in april this year, apart from that it's >fullwidth not possible given the way it was implemented with all the >conditions and extensions. > >Deep thoughtII searched many tens of millions nodes a second and got 10 ply. >deep blue was more NPS optimized, and got just a ply or at most 2 ply >deeper. very logical. DTII searched 750k NPS. DB searched about 100M NPS, while DB2 does about twice that. DTII also had a much smaller evaluation than DB/DB2, and I assume it extended less, as well.
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