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#Post#: 63--------------------------------------------------
The Planchet Program for playing Musketeer Chess
By: GothicChessInventor Date: January 13, 2018, 3:36 pm
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I loaded the 3-piece tables into a RAM buffer, and wanted to
test to see if my Musketeer Chess program, Planchet, was able to
use them correctly. You might find this interesting.
[attachimg=1]
The position above is white to move.
The program was able to announce a Mate in 57-ply in about 2
seconds:
[attachimg=2]
You can see it played QxA KxQ and what remains is a 3-piece
tablebase position it knows is a win in 55-ply from the longest
win in the Hawk vs. King tablebase.
When I turn off the tablebase probing in RAM, this is how it
plays:
[attachimg=3]
It just wants to save the Hawk being menaced by the Archbishop.
What a profound difference in play!
#Post#: 69--------------------------------------------------
Re: The Planchet Program for playing Musketeer Chess
By: chilipepper Date: January 13, 2018, 11:59 pm
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Interesting. What source do you use to for the definition of
Musketeer chess pieces?
Is it this:
HTML http://musketeerchess.net/games/musketeer/rules/rules-short.php
?
#Post#: 70--------------------------------------------------
Re: The Planchet Program for playing Musketeer Chess
By: GothicChessInventor Date: January 14, 2018, 12:04 am
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[quote author=chilipepper link=topic=22.msg69#msg69
date=1515909589]
Interesting. What source do you use to for the definition of
Musketeer chess pieces?
Is it this:
HTML http://musketeerchess.net/games/musketeer/rules/rules-short.php
?
[/quote]
I computed values based on the experiences learned from the
paper I published when I had to derive new piece values for the
10x8 board for Gothic Chess back in the year 2000. I posted a
topic showing some of the geometry and algebra used to make a
derivation for a Rook on a rectangular board of any dimension,
along with a link where you can download the paper.
#Post#: 72--------------------------------------------------
Re: The Planchet Program for playing Musketeer Chess
By: GothicChessInventor Date: January 14, 2018, 12:17 am
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I decided to make a coding change to the program. This is the
result:
[attachimg=1]
I noticed that the prior version of the program stopped
searching shortly after finding a path into the online tablebase
probed in RAM during the search. Originally I thought this was
awesome; finding a mate in 29 moves after only a 5-ply search.
Then it dawned on me: 5-ply means it only generated 3 moves for
white (2 for black) so technically, the program could be passing
up a mate in 4 by quitting the search early! In fact, there
could be mates in 4, 5, 6, 7, ...up to 28 that the program could
potentially "miss" if I have it stop once a proven path to the
tablebase is found.
So I modified to search so that the DEPTH of search is allowed
to increase until "Mate in x" is announced, where d = 2x - 1.
Usually you never have to worry about this, because the depth at
which the mate is discovered is usually the same as the depth of
the current search's iteration, but with tablebases probed in
RAM, the "checkmate sight" is much greater than the depth of
search.
Bearing that in mind, take a look at the lines of play the
program found. At first, I did not understand them, but once it
became apparent what the lines of play represented, it was
hilarious!
At depth 5 the program wants to throw away its queen to remove
the archbishop, and in so doing forces the black king onto a
square corresponding to a 3-piece tablebase position where it is
white to move and win in 55-ply. Since that position is 2-ply
distant, the program correctly reports that QxA+ KxQ is a mate
in 57-ply.
Then the program announces a mate in 55-ply without the
sacrifice. My first thought was: Bug in the program! But this is
not the case. The program plays the Hawk to d4 to avoid having
it captured trivially by the black archbishop. Then black
appears to make the stupid move ...Ke6 which keeps it on the
c8-h3 diagonal where it will be checked by the white queen while
losing the archbishop at the same time. Why the heck would the
program allow such bad play? Well, by spending a move to run
away, black costs white a move to "force" the capture of the
archbishop with the queen, and because black does not recapture
the queen, the program has not entered into the mate in the
tablebase. Being down an archbishop is better than being
checkmated within a known horizon. So the black king allows the
check and starts running away. But white resumes chasing with
the queen, which he eventually throws away! The line of play
that is produced shows black getting his king onto the square
resulting in the longest loss in the Hawk endgame tablebase and
white engineers queen moves to try and minimize the desperato
effort to toss the queen. It is rather funny. Black is running
away, trying to avoid "winning a queen," and white chases him
down anyway, and "forces" black to capture the queen. The result
is a delayed entry into the tablebase, but a shorter tablebase
path to victory, netting a 2-ply reduction from 57-ply to
55-ply.
And then it happens again! At depth 9, white found a sequence to
reduce the overall win to 53-ply, although the play seems more
logical to humans. With Qc5 white defends the Hawk, "daring" the
archbishop to take it and enter into a rapid loss in the queen
vs. king tablebase. Black can only alter the square on which the
king will reside in the Hawk tablebase again, so with Ae7 Qxe7+
Kxe7 that is what happened, with a 53-ply mate announced.
#Post#: 85--------------------------------------------------
Re: The Planchet Program for playing Musketeer Chess
By: GothicChessInventor Date: January 15, 2018, 11:53 am
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And, amazingly, by prioritizing tablebase probes to quiescence,
and by just letting it search one ply deeper, it found a mate in
21-ply that cannot be avoided. It also improved the depth-09
assessment by the time it completed that iteration.
[attachimg=1]
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