is a game by Christian Freeling. Java applet © 1997 Ed van
Caïssa is a sort of chess game that was published
first on www.mindsports.net.
for the playing rules. I competed with an own version at the CodeCup
2003. My program is called HIPP and is made in C. You can download
a project version and study it. For the calculation of the best
move HIPP uses the MTD(f)
algorithm. This algorithm uses the constant calling of alfabeta
pruning (without memory function) with a so called zero-window
search. I have limited the range from the evaluation function
from -25 tot 25 to reduce the number of calls. The algorithm is
called iteratively to calculated a move one step deeper each time.
In the beginning it is not necessary to check for the connection
rule and HIPP searches four levels deep. In the end-game the connection
rule needs to be checked and HIPP searches for three levels deep.
After a quicksort of the possible moves HIPP calculates the best
five moves one step deeper. By using a fast generator for moves
HIPP finds for each position in the beginning ± 3 million
moves. About 30.000 moves are actually executed and 27.000 positions
are evaluated. That takes about ± 3 seconds. I have implemented
more ideas and I have descibed them in a PDF-document. You can download
the document, print and read it. A short summarize:
- If in a certain position check is given, HIPP calculates
one step deeper from that point because in such a situation
the number of countermoves is limited. If in the beginning game
two or three moves are available the situation is also calculated
one step deeper. Due to this a checkmate situation is found
at ten levels deep. In this way I guess that HIPP searches effectively
for six to seven levels deep.
- The basic idea for the evaluation function is simple and
fast: Value= NumberMovesOfMyself - NumberMovesOfOpponent. For
this the number of moves from the opponent from the called level
is used. I have a big advantage if my opponent is given check!
- The first four moves from white and the first three moves
of white are calculated in advance. The making of the opening
book took about three weeks on a 850 MHz-machine. By calculating
the opening moves by more than ten levels deep secures a safe,
fast and favourable opening.