[computer-go] How to cache local tactical searches?

[Chrilly]

One can not use a global hash-code but a local one. E.g. a hashcode of the 
smallest "dirty" region. Calculating the hashcode during the local search is 
easy. But then one has to know which area is involved and calculate the 
hashcode of this board-area (which is expensive). Another Possibility is to 
make a partition of the board into tiles. E.g. 5x5 or 4x4 and to have for 
every tile a hashcode. The local-hash code is the XOR of the dirty tiles. 
One has additionally store the info which tiles are dirty. E.g. as a bitset. 
As usually only a few tiles are involved these calculations should be 
relative fast.

Chrilly


> Instead of a bitmap you should use a hash-key of course, the
> comparison is much cheaper.
>
> Mark
>