WCC is capable of playing every position
with 7 or fewer pieces perfectly.
What does this mean? When WCC is in a winning
position, it will always converge on the win in the quickest manner possible.
It knows exactly how many moves are required to reach the last move of the
game for every position in its database. So, when WCC plays the winning
side, it generates every legal move, then queries the database to get the
total number of moves remaining in the game after the move is made. WCC then
selects the move leading to the quickest win.
If you set up WCC to play a position that is
a loss, it will query the database and select the move that leads to the most
distant loss possible, thereby dragging out the game.
Is it possible to be in a won position and
not win against WCC? Yes! Can WCC be in a loss and still hold a draw? Yes!
Is it possible for WCC to be in a won position in its PPL database and not
WCC played two friendly experimental games
with the Wyllie program to test how the perfect play database could defend
a "lost" position. One position was the most distant win possible in which
the losing side cannot set up a Fourth Position draw. This position is hard
for a human to win, but because the path to the win is punctuated with positions
in which there is only one move to win, the Wyllie program was able to eventually
find the win.
In the second game, WCC again played the losing
side of a 7-piece position, and Wyllie was not able to win the game.
WCC also played the Kingsrow program in three
experimental games. On the winning side, Kingsrow was unable to win against
the powerful perfect play lookup database. At the point where Kingsrow allowed
the draw, WCC took over, now playing the strong side against Kingsrow. WCC
was able to win this game easily. Kingsrow programmer Ed Gilbert found some
code in his program that was in need of changing to avoid a "repetition draw,"
so about two weeks later a third game was played. Kingsrow was unable to
win that game either.
You might be aware of what is referred to as
a "conversion" database. How does a "conversion database compare to a perfect
play database? The answer is: A conversion database is vastly inferior
to a perfect play lookup database. In fact, a conversion database can be
worse than no database at all when it comes to playing a position!
A classic example from the 3-piece database
demonstrates the extreme deficiencies of a conversion database.
Every novice player on the planet can immediately
identify with a casual glance that 15-18 is the best and quickest move to
win, forcing the king up against the side of the board and capturing him
in only five moves. But a conversion database will prefer to "convert"
by advancing the checker with 21-25??? and crowning on the next move, leading
to a long, drawn-out win as the opponent's king escapes into the double corner.
The reason for this is that a conversion database
always thinks that the best way to win is to either trade pieces or promote
kings (that is, to "convert" to a position with a different combination of
pieces). As long as it preserves the win, a conversion database will blindly
make foolish moves. To a conversion database, the move 15-18 takes too
long to convert, even though the conversion is a game-ending win, which
it does not know, unlike a PPL database. The move 25-21 converts the checker
into a king more quickly than 15-18 converts to the game's conclusion, therefore,
the foolish and wasteful move 25-21 will be played by a conversion database.
If the conversion database were turned off in this position, a simple search
by the program would find the best move instantaneously. Thus, in this example,
a conversion database is far worse than no database at all!
The major difference between the perfect play
lookup (PPL) database and the conversion database is this: The PPL database
actually knows when the game is over! For this reason, no matter where you
are in a game, the PPL database will always converge on wins most quickly,
and push losses as far away as possible, often frustrating the opponent into
conceding a draw.
WCC's PPL database is the only database that
plays perfectly every time.