Author: Stuart Cracraft
Date: 21:43:27 09/02/04
So today I find out that my recapture is bad. It must be. Bob said so.
I take 1 minute to reimplement it to be "extend on 2nd capture on the same
square in a row" because I heard someone else talking about that's the
way they do it and got a surprise a minute after that.
The result is that Qxf4 for Win-at-Chess comes into view
in 98 seconds and holds after having been missed after seemingly
endless runtime with the old bad recapture in or out. Of course
it is nothing like the 13,000 nodes that Tord (was it?) solves
141 in. Perhaps we should have a contest for who solves 141 in
the fewest moves. He would surely win. It takes me 24 million.
I admire a search that is so directed in so few nodes. Surely
we pay homage to Berliner with it, eh? Retire in peace in Florida
and then two category 4 storms hit. Unlucky fellow.
Alpha=-1182 Beta=-682 Maxdepth=9999999 MaxTime=100000
1/13 g2f1 0.01 -953 945 g2f1 f4d5
2/13 g2f1 0.01 -953 1535 g2f1 f4d5 c1g5
3/15 g2f1 0.02 -953 5010 g2f1 f4d5 c1g5 d5f6
4/23 g2f1 0.09 -953 21387 g2f1 f4d5 b3d5 c6d5 c1c7 d6c7 f1g1
5/25 g2f1 0.65 -953 179404 g2f1 b5b4 b3a4 f4d5 f6g5 d5e7
6/44 g2f1 3.15 -953 728459 g2f1 b5b4 b3a4 f4d5 f6g5 d5e7
7/48> g2f1 64.75 -703 15048349 g2f1 e8c8 f1g1 c8e8 c1b1 f4e2 g1g2 e2d4
7/48 c1f4 98.86 5113 24322991 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7
8/48< c1f4 98.88 4863 24327933 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7
8/48 c1f4 108.60 4863 26455348 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7
9/48> c1f4 159.87 5113 38207334 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7
I know my PV is screwy and wonder why Bxf4 isn't played next. Anyone
know why? To me, Qxf4 followed by Bxf4 and then rook taking along the
H file looks like the natural PV. I wonder if that is another nasty
bug lurking. I am surprised there can be so many remaining considering
a fairly decent run-of-the-mill score on WAC 1-300. The set seems to
have shortcomings. Good for a first year's development effort though.
I am not able to speed 141 up yet with Moreland's Mate Threat Null extension nor
Botvinnik-Markoff's extension, but hopefully those will help, though they
haven't so far. Nor did using checking moves in the quiescence search.
None of those three has improved the time of the above, for me. I haven't
tried leaving out all check evasion moves in the main search and quiescence
search which speeds up the program tons but makes tactical solution rates
suffer.
New recapture tested just slightly less than 1% worse in score on Win-at-Chess
for me but is solid enough to be okay to keep as a permanent setting.
My recaptures happen at any level and there is no limit -- perhaps that
is not great. I should reread the archives and try to find Bob's earlier
recapture description.
I see in Crafty 19.16 that he has this which I hadn't looked at,
having just heard someone else talking about capture to square
then capture to second square, but I didn't put in the material
score being restored so perhaps I got lucky or there's some
further speedup to be gained by the addition of the material
score requirement. (Btw, looking at Crafty, or GNU, or any
other better program, to me is a form of cheating. I don't
like doing it. I don't like the feeling I get after doing it,
and I refuse to do it more than very infrequently.)
/*
************************************************************
* *
* if two successive moves are capture / re-capture so *
* that the material score is restored, extend the search *
* by one ply on the re-capture since it is pretty much *
* forced and easy to analyze. *
* *
************************************************************
*/
recapture = 0;
if (!extended && Captured(tree->current_move[ply - 1]) &&
To(tree->current_move[ply - 1]) == To(tree->current_move[ply]) &&
(p_values[Captured(tree->current_move[ply - 1]) + 7] ==
p_values[Captured(tree->current_move[ply]) + 7] ||
Promote(tree->current_move[ply - 1])) && !lp_recapture) {
tree->recapture_extensions_done++;
extended += recap_depth;
recapture = 1;
}
Cheers,
Stuart
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