Author: David Eppstein
Date: 22:52:51 05/30/99
Go up one level in this thread
On May 30, 1999 at 08:29:56, Robert Hyatt wrote:
>On May 29, 1999 at 23:31:38, Jeremiah Penery wrote:
>>Someone wrote a fix for this and it was posted in the Crafty mailing list...I
>>haven't payed much attention to whether it works always/sometimes/never, or
>>whether it works very well, but it *seemed* to solve the problem.
>>It'll make Crafty drop out of TBs if there is a good promotion move, but there
>>is no TB for the promotion.
>
>It isn't simple, because I do things like stop the extra parallel threads when
>in a tablebase position, etc. Searching the odd promotions would take a little
>thought as we would want those threads back..
>
>And the main point is, _why_? Because it will screw up the normal search
>since a P on the board says mate in N, but a Q on the board doesn't say mate.
>This means a search from a position where the promotion can be forced many
>plies into the tree looks like a bad move to the search.
>
>Again, get 'em all, or don't get the P database in question...
As Jeremiah wrote, it should no longer be necessary to get all the tablebases
for all the easy promotion cases, since it is possible to use code similar to
your "swindle mode" to make a good move from a tablebase to a non-tablebase
position.
Tim Hollebeek posted code for this to the Crafty mailing list on February 27,
with a correction March 10. I'm enclosing a portion of his message below since
the technique may be of interest for other programs:
From: Tim Hollebeek <tim@wagner.princeton.edu>
To: David Eppstein <eppstein@ics.uci.edu>
Cc: crafty@jpunix.com
Subject: Re: [crafty] TB Question
Date: Sat, 27 Feb 1999 11:19:16 -0500 (EST)
David Eppstein writes ...
>
> This does sound like a better idea. So the algorithm would be:
>
> if (you're currently in a tablebase position where you can promote &&
> the tablebase for the position after the promotion is missing &&
> your current score is mate-in-n &&
> none of the non-promotion moves lead to mate-in-(n-1))
> then do a search restricted to the promoting moves.
>
> Crafty's swindle mode already does a similar constrained search, how much
> more work could another one be?
Thanks for the idea. I looked at the swindle code, and found it is
very easy to do "the right thing" in RootMoveList(), instead of fiddling
with SearchRoot() like my previous hack.
This one is much more elegant and, more importantly, has no obvious holes.
It turns out that RootMoveList() already does the necessary EGTB
checks due to the swindle code. My patch looks at the score of the
current position, and if it is a EGTB mate, figures out what the score
of the "correct" next move is. From the way the EGTBs are generated,
we know a move exists that has that score.
Now, when generating the move list, we discard all moves that (1) are
in the EGTB, but (2) have a score worse than the expected score. The
EGTB is telling us this is *not* the right move, despite the fact it
is a mate.
Now there are two cases:
#1: we do have the TB that contains the continuation of the mate. In
this case the correct move is in the root move list, and it is
impossible for any other move to have a better score. So discarding
"worse" moves has no effect on which move is played.
#2 (the important case): the "correct" move is a capture or promotion
moves us to a TB we don't have. In this case, our root move list
consists only of moves that leave the TB. This is very likely to find
the "correct" move, since the only way it can fail is positions which
have more than one move that leaves the TB, one which wins, the
other(s) which draw or lose, and it isn't obvious to a search which is
best. Such positions would be rather fascinating, but probably
exceedingly rare.
Attached is a diff, and an example of crafty playing a position (with
KNKP) it often screws up if it doesn't have the KNKQ TB. Note that
crafty plays the obvious move "b1=Q" at the correct point, instead of
moving its king around aimlessly.
[ diff deleted - DE 5/30/99 ]
---
EPD Kit revision date: 1996.04.21
unable to open book file [./book.bin].
book is disabled
unable to open book file [./books.bin].
Crafty v16.5
White(1): egtb 4
EGTB access enabled
using tbpath=./TB
4 piece tablebase files found
54kb of RAM used for TB indices and decompression tables
White(1): ponder off
pondering disabled.
White(1): level 0 1 1
game/1 minutes primary time control
increment 1 seconds.
White(1): setboard KN/////kp b
Black(1): go
end-game phase
clearing hash tables
time limit 2.71 (16.26) [easy move]
depth time score variation (1)
4 0.05 Mat15 1. ... b2 2. Kb7 Kb4 <EGTB>
4-> 0.05 Mat15 1. ... b2 2. Kb7 Kb4 <EGTB>
time=0.18 cpu=16% mat=-2 n=494 fh=77% nps=2744
ext-> checks=43 recaps=0 pawns=5 1rep=0
predicted=0 nodes=494 evals=24
endgame tablebase-> probes done=46 successful=16 plimit=6
hashing-> trans/ref=34% pawn=96% used=0%
mate in 15 moves.
Black(1): b2
time used: 0.18
White(2): go
clearing hash tables
time limit 2.73 (16.38)
depth time score variation (1)
10 0.67 -Mat14 2. Nc6 Ka4 3. Kb7 <EGTB>
10-> 0.67 -Mat14 2. Nc6 Ka4 3. Kb7 <EGTB>
11 2.59 -Mat14 2. Nc6 Ka4 3. Kb7 <EGTB>
11-> 2.59 -Mat14 2. Nc6 Ka4 3. Kb7 <EGTB>
time=2.95 cpu=91% mat=2 n=77662 fh=98% nps=26326
ext-> checks=11587 recaps=3 pawns=0 1rep=231
predicted=0 nodes=77662 evals=63
endgame tablebase-> probes done=10035 successful=337 plimit=16
hashing-> trans/ref=67% pawn=98% used=4%
mated in 14 moves.
White(2): Nc6
Black(2): go
clearing hash tables
time limit 2.68 (16.08)
depth time score variation (1)
time=0.30 cpu=56% mat=-2 n=4510 fh=95% nps=15033
ext-> checks=480 recaps=0 pawns=20 1rep=32
predicted=0 nodes=4510 evals=1
endgame tablebase-> probes done=486 successful=0 plimit=8
hashing-> trans/ref=96% pawn=0% used=0%
Black(2): b1=Q
White(3): go
clearing hash tables
time limit 2.70 (16.20)
depth time score variation (1)
6 0.58 -7.00 3. Nb8 Ka4 4. Ka7 Qb2 5. Ka8 Ka5
6-> 0.62 -7.00 3. Nb8 Ka4 4. Ka7 Qb2 5. Ka8 Ka5
7 0.92 -7.11 3. Nb8 Ka4 4. Ka7 Ka5 5. Nc6+ Kb5 6.
Nd8 Kc5
7-> 1.74 -7.11 3. Nb8 Ka4 4. Ka7 Ka5 5. Nc6+ Kb5 6.
Nd8 Kc5
8 2.18 -7.11 3. Nb8 Ka4 4. Ka7 Ka5 5. Nc6+ Kb5 6.
Nd8 Qh7+ 7. Kb8 Ka6
8-> 2.36 -7.11 3. Nb8 Ka4 4. Ka7 Ka5 5. Nc6+ Kb5 6.
Nd8 Qh7+ 7. Kb8 Ka6
time=2.87 cpu=90% mat=-6 n=68235 fh=88% nps=23775
ext-> checks=9689 recaps=0 pawns=0 1rep=276
predicted=0 nodes=68235 evals=1
endgame tablebase-> probes done=12120 successful=0 plimit=13
hashing-> trans/ref=79% pawn=0% used=4%
White(3): Nb8
Black(3): go
clearing hash tables
time limit 2.64 (15.84)
depth time score variation (1)
6-> 0.47 7.11 3. ... Ka4 4. Ka7 Qb5 5. Ka8 Ka5 6.
Ka7
7 0.63 7.11 3. ... Ka4 4. Ka7 Qb5 5. Ka8 Ka5 6.
Ka7 Qb1
7-> 0.96 7.11 3. ... Ka4 4. Ka7 Qb5 5. Ka8 Ka5 6.
Ka7 Qb1
8 1.32 7.11 3. ... Ka4 4. Ka7 Qb5 5. Ka8 Ka5 6.
Ka7 Qd5 7. Na6
8 2.68 ++ 3. ... Qb6!!
time=2.81 cpu=91% mat=6 n=70507 fh=94% nps=25091
ext-> checks=11343 recaps=0 pawns=0 1rep=240
predicted=0 nodes=70507 evals=1
endgame tablebase-> probes done=10235 successful=0 plimit=12
hashing-> trans/ref=91% pawn=0% used=3%
Black(3): Qb6
White(4): go
clearing hash tables
time limit 2.59 (15.54) [easy move]
depth time score variation (1)
6 0.70 -9.85 4. Nd7 Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Kb4
7. Kb6 Qc8
6-> 0.73 -9.85 4. Nd7 Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Kb4
7. Kb6 Qc8
7 1.33 -10.08 4. Nd7 Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6
7-> 1.36 -10.08 4. Nd7 Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6
8 2.62 -10.11 4. Nd7 Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6 Qb5+ 9. Ka7 Ka5
time=2.75 cpu=91% mat=-6 n=70063 fh=99% nps=25477
ext-> checks=13617 recaps=0 pawns=0 1rep=344
predicted=0 nodes=70063 evals=1
endgame tablebase-> probes done=4335 successful=0 plimit=10
hashing-> trans/ref=94% pawn=0% used=3%
White(4): Nd7
Black(4): go
clearing hash tables
time limit 2.54 (15.24)
depth time score variation (1)
5 0.56 9.85 4. ... Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Kb4
7. Kb6 Qc8
5-> 0.71 9.85 4. ... Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Kb4
7. Kb6 Qc8
6 1.04 10.08 4. ... Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6
6-> 1.35 10.08 4. ... Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6
7 2.25 10.11 4. ... Qc6+ 5. Ka7 Qxd7+ 6. Ka6 Ka4
7. Kb6 Kb4 8. Ka6 Qb5+ 9. Ka7 Ka5
time=2.70 cpu=88% mat=6 n=65868 fh=99% nps=24395
ext-> checks=12969 recaps=0 pawns=0 1rep=302
predicted=0 nodes=65868 evals=1
endgame tablebase-> probes done=4576 successful=0 plimit=11
hashing-> trans/ref=109% pawn=0% used=91%
Black(4): Qc6+
White(5): go
clearing hash tables
time limit 2.49 (14.94)
depth time score variation (1)
5 0.52 -9.85 5. Ka7 Qxd7+ 6. Ka6 Kb4 7. Kb6 Qc8
5-> 0.52 -9.85 5. Ka7 Qxd7+ 6. Ka6 Kb4 7. Kb6 Qc8
6 0.87 -10.08 5. Ka7 Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6
6-> 0.89 -10.08 5. Ka7 Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6
7 1.80 -10.11 5. Ka7 Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6 Qb5+ 9. Ka7 Ka5
7-> 1.81 -10.11 5. Ka7 Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6 Qb5+ 9. Ka7 Ka5
time=2.67 cpu=91% mat=-6 n=67947 fh=99% nps=25448
ext-> checks=13939 recaps=0 pawns=0 1rep=281
predicted=0 nodes=67947 evals=1
endgame tablebase-> probes done=2006 successful=0 plimit=9
hashing-> trans/ref=104% pawn=0% used=3%
White(5): Ka7
Black(5): go
clearing hash tables
time limit 2.45 (14.70)
depth time score variation (1)
4 0.45 9.85 5. ... Qxd7+ 6. Ka6 Kb4 7. Kb6 Qc8
4-> 0.52 9.85 5. ... Qxd7+ 6. Ka6 Kb4 7. Kb6 Qc8
5 0.80 10.08 5. ... Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6
5-> 0.90 10.08 5. ... Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6
6 1.70 10.11 5. ... Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6 Qb5+ 9. Ka7 Ka5
6-> 1.88 10.11 5. ... Qxd7+ 6. Ka6 Ka4 7. Kb6 Kb4
8. Ka6 Qb5+ 9. Ka7 Ka5
time=2.57 cpu=89% mat=6 n=61042 fh=99% nps=23751
ext-> checks=12546 recaps=0 pawns=0 1rep=257
predicted=0 nodes=61042 evals=1
endgame tablebase-> probes done=6607 successful=0 plimit=11
hashing-> trans/ref=114% pawn=0% used=5%
Black(5): Qxd7+
White(6): go
clearing hash tables
time limit 2.40 (14.40)
depth time score variation (1)
4 0.43 -9.85 6. Ka6 Kb4 7. Kb6 Qc8
4-> 0.43 -9.85 6. Ka6 Kb4 7. Kb6 Qc8
5 0.69 -10.08 6. Ka6 Ka4 7. Kb6 Kb4 8. Ka6
5-> 0.73 -10.08 6. Ka6 Ka4 7. Kb6 Kb4 8. Ka6
6 1.51 -10.11 6. Ka6 Ka4 7. Kb6 Kb4 8. Ka6 Qb5+ 9.
Ka7 Ka5
6-> 1.52 -10.11 6. Ka6 Ka4 7. Kb6 Kb4 8. Ka6 Qb5+ 9.
Ka7 Ka5
time=2.51 cpu=90% mat=-9 n=63254 fh=99% nps=25200
ext-> checks=13409 recaps=0 pawns=0 1rep=217
predicted=0 nodes=63254 evals=1
endgame tablebase-> probes done=5455 successful=0 plimit=9
hashing-> trans/ref=112% pawn=0% used=2%
White(6): Ka6
Black(6): go
clearing hash tables
time limit 2.36 (14.16)
depth time score variation (1)
5 0.46 10.11 6. ... Ka4 7. Kb6 Kb4 8. Ka6 Qb5+ 9.
Ka7 Ka5
5-> 1.35 10.11 6. ... Ka4 7. Kb6 Kb4 8. Ka6 Qb5+ 9.
Ka7 Ka5
6 1.67 10.08 6. ... Ka4 7. Kb6 Kb4 8. Ka6 Qc6+ 9.
Ka7 Qc7+ 10. Ka6 Kc4
time=2.66 cpu=91% mat=9 n=67550 fh=99% nps=25394
ext-> checks=14374 recaps=0 pawns=0 1rep=204
predicted=0 nodes=67550 evals=1
endgame tablebase-> probes done=6947 successful=0 plimit=9
hashing-> trans/ref=111% pawn=0% used=5%
Black(6): Ka4
White(7): go
clearing hash tables
time limit 2.31 (13.81) [easy move]
depth time score variation (1)
time=0.21 cpu=38% mat=-9 n=1760 fh=99% nps=8380
ext-> checks=378 recaps=0 pawns=0 1rep=10
predicted=0 nodes=1760 evals=1
endgame tablebase-> probes done=258 successful=0 plimit=7
hashing-> trans/ref=117% pawn=0% used=2%
White(7): Kb6
Black(7): go
clearing hash tables
time limit 2.33 (13.98)
depth time score variation (1)
5 0.55 ++ 7. ... Kb4!!
5 0.55 Mat03 7. ... Kb4 8. Ka6 Kc5 9. Ka5 Qb5#
5-> 1.31 Mat03 7. ... Kb4 8. Ka6 Kc5 9. Ka5 Qb5#
time=1.44 cpu=86% mat=9 n=34779 fh=99% nps=24152
ext-> checks=7547 recaps=0 pawns=0 1rep=170
predicted=0 nodes=34779 evals=1
endgame tablebase-> probes done=2819 successful=0 plimit=9
hashing-> trans/ref=104% pawn=0% used=1%
mate in 3 moves.
Black(7): Kb4
White(8): go
clearing hash tables
time limit 2.32 (13.91) [easy move]
depth time score variation (1)
time=0.31 cpu=51% mat=-9 n=4614 fh=99% nps=14883
ext-> checks=853 recaps=0 pawns=0 1rep=67
predicted=0 nodes=4614 evals=1
endgame tablebase-> probes done=268 successful=0 plimit=6
hashing-> trans/ref=126% pawn=0% used=87%
mated in 2 moves.
White(8): Ka6
Black(8): go
clearing hash tables
time limit 2.34 (14.04)
depth time score variation (1)
3 0.05 Mat02 8. ... Kc5 9. Ka5 Qb5#
3-> 0.20 Mat02 8. ... Kc5 9. Ka5 Qb5#
4 0.21 Mat02 8. ... Kc5 9. Ka5 Qb5#
4-> 0.75 Mat02 8. ... Kc5 9. Ka5 Qb5#
time=0.88 cpu=78% mat=9 n=19571 fh=100% nps=22239
ext-> checks=3936 recaps=0 pawns=0 1rep=178
predicted=0 nodes=19571 evals=1
endgame tablebase-> probes done=449 successful=0 plimit=5
hashing-> trans/ref=114% pawn=0% used=0%
mate in 2 moves.
Black(8): Kc5
White(9): go
clearing hash tables
time limit 2.34 (14.04) [easy move]
depth time score variation (1)
time=0.21 cpu=38% mat=-9 n=2132 fh=100% nps=10152
ext-> checks=404 recaps=0 pawns=0 1rep=33
predicted=0 nodes=2132 evals=1
endgame tablebase-> probes done=127 successful=0 plimit=6
hashing-> trans/ref=58% pawn=0% used=3%
mated in 1 moves.
White(9): Ka5
Black(9): go
clearing hash tables
time limit 2.37 (14.22)
depth time score variation (1)
1 0.00 ++ 9. ... Qb5#!!
1 0.00 Mate 9. ... Qb5#
1-> 0.01 Mate 9. ... Qb5#
2 0.01 Mate 9. ... Qb5#
2-> 0.03 Mate 9. ... Qb5#
3 0.03 Mate 9. ... Qb5#
3-> 0.11 Mate 9. ... Qb5#
4 0.11 Mate 9. ... Qb5#
4-> 0.35 Mate 9. ... Qb5#
time=0.48 cpu=60% mat=9 n=8453 fh=99% nps=17610
ext-> checks=1629 recaps=0 pawns=0 1rep=94
predicted=0 nodes=8453 evals=1
endgame tablebase-> probes done=396 successful=0 plimit=6
hashing-> trans/ref=74% pawn=0% used=0%
Black(9): Qb5#
0-1 {Black mates}
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