Author: Ricardo Gibert
Date: 07:15:33 04/18/03
Go up one level in this thread
On April 18, 2003 at 09:33:15, Robert Hyatt wrote: >On April 18, 2003 at 01:36:20, Ricardo Gibert wrote: > >>On April 17, 2003 at 10:42:23, Robert Hyatt wrote: >> >>>On April 16, 2003 at 20:22:26, Ricardo Gibert wrote: >>> >>>>On April 16, 2003 at 20:01:19, J. Wesley Cleveland wrote: >>>> >>>>>On April 16, 2003 at 14:30:03, Robert Hyatt wrote: >>>>> >>>>> >>>>>>No you can't. You _always_ have to search every move at the root. that is the >>>>>>_only_ node where you can make that statement. >>>>> >>>>>ob_nitpick: If the position is mate in 1, then you only need to search the >>>>>mating move. >>>> >>>> >>>>I already pointed this out. In fact, this is true for any odd depth ending in >>>>mate as per Knuth/Moore. RH wants to dismiss this as uncommon, while avoiding >>>>admitting the statement, "You _always_ have to search every move at the root" is >>>>false. >>> >>> >>>OK. In a normal game, in 99.999999999999999999999999999999999999999999999% of >>>the positions, you have to search _all_ moves at the root. >>> >>>Is that better? >>> >>>I just looked at 200 games with GM players vs Crafty. Not a _single_ game ended >>>with >>>mate in 1 by Crafty. The GM resigned when he saw a mate coming. >>> >>>I don't _care_ about non-root positions, because if you notice, the discussion >>>was about >>>splitting the parallel search at the _root_. Everybody splits below the root so >>>that's moot. >>>But at the root, it isn't. And I would call >>>99.99999999999999999999999999999999999999999999% close enough to 100% to say >>>"all root positions". >>> >>>It is _far_ more likely to find a position with only one legal move at the root, >>>but then the >>>discussion is moot again because there is no opportunity to split at the root. >>> >>>I'm not sure why the "nit-pick" is so very important... >> >>(1) It's important, because you present as true the statement, "You _always_ >>have to search every move at the root", which is false. This is clear, because >>you emphasize with "_always_". >> >>(2) It's important, because mate in 1 is only the most obvious example. The same >>thing holds for mate in 3 plys, mate in 5 plys, mate in 7 plys, mate in 9 plys, >>etc. All according to Knuth/Moore BTW. > >This is wrong. If I find a mate in 3 plies I can't stop. I have to search to >be sure there >isn't a shorter mate, which at least means a complete pass thru the root moves.. If what you are talking about is finding this mate in 3 plys, because of extensions or qsearch, it might still be possible to find a shorter mate, since there could still be a mate in 1 ply or you might even get mated in 2 plys. However, if you are using iterative deepening and you are currently searching to a depth of 3 and you find a mate in 3 plys, there is no point in searching other root moves. Because of iterative deepening, you have already eliminated the shorter mates. Your "This is wrong" puts you in opposition to Knuth/Moore. Maybe you should write them and explain to them where they went wrong? ;) > > >> >>(3) It's important, because it is not as rare as you seem to think. > >No times in 200 games, where each game averaged 60 moves long. 12,000 root >positions to be searched, one where there was a mate in 1 found. > >I call that "not important at all". > > >> >>If your engine ever searches to an odd depth and if the evaluation of the root >>position is supposed to be +infinity, then your engine does not need to search >>all the moves at the root. > > >And exactly when will that happen? Only on a mate in 1 for me, and against good >players it just doesn't happen... > >I searched through 4,000 games last night, looking for "#" indicating that there >was a >mate in one in the game. I found seven. All appeared to be unexpected and >happened when >the GM was _very_ short on time so that he probably didn't notice he was making >a bad >mistake. > >I therefore conclude that when talking about splitting at the root, my statement >"you always >search all legal moves at the root" is quite accurate. If you'd prefer, I'm >more than happy to >change it to "in 99.825% of the cases, you will have to search all root moves." >But, in light >of parallel search, 99.825 is 100%.
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