Author: Ricardo Gibert
Date: 22:36:20 04/17/03
Go up one level in this thread
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. (3) It's important, because it is not as rare as you seem to think. 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.
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