Re: [gnugo-devel] pattern-based reading spinoffs (27.7)

[Gunnar Farneback]

Dan wrote:
> Actually it looks to me as if 9 bits would be large enough
> for kom_pos if MAX_BOARD is at most 19 so BOARDSIZE <= 421 < 2^9.
> This means that we could add one bit to komaster unless I'm 
> missing something.

BOARDSIZE isn't relevant since we would never need to cache any value
larger than BOARDMAX. But if we want to make the komaster field one
bit larger it would be much easier to just extend it. From cache.h:

 * The data1 field packs into 32 bits the following
 * fields:
 *
 * komaster:  2 bits (EMPTY, BLACK, WHITE, or GRAY)
 * kom_pos : 10 bits (allows MAX_BOARD up to 31)
 * routine :  4 bits (currently 10 different choices)
 * str1    : 10 bits
 * stackp  :  5 bits

These sum to 31, so there is space to extend komaster to 3 bits
without sacrificing anything more than available space for other
potential needs.

/Gunnar