Description:

Sirius is a program for playing the game of reversi. The program includes an AI
(Artificial Intelligence) opponent which plays at a very challenging level and
is actually quite hard to beat. The AI opponent's strength can therefore be
adjusted in several ways to give you a suitable opponent.

The AI opponent uses a plain alpha-beta search with hashing to figure out which
move to make. To be able to tell a good position from a bad one, it uses a
pattern based evaluation function. The pattern used is the 9 discs surrounding
each corner and the 8 discs creating the edge of the board. The evaluation
function also takes mobility, potential mobility and parity into count. For the
initial 9 moves the AI opponent optionally uses a simple opening book. During
midgame it searches and evaluates about 200.000 nodes per second on a PIII
750 MHz, in the endgame this number is significantly higher due to more
transpositions and a less expensive evaluation function.