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

[Daniel Bump]

An issue in the komaster scheme is that you will need to pack
the information into as few bits as possible, because this
needs to be cached in the Zobrist hashing. Currently 2 bits
are available.

Some of the defects of the current scheme could be ameliorated
if we allowed more than 4 values for the komaster. Even one
more bit would allow a more flexible scheme. This would require some
rearrangement of the data field of the hash node.

This issue came up fairly recently in connection with the patch
komaster_1_22.1. Gunnar proposed around this time to switch to
one of the other schemes, which I did not want to do. I think
Gunnar's final word on this issue is:

http://mail.gnu.org/pipermail/gnugo-devel/2002-January/001123.html

I wasn't convinced by this but clearly this is an open topic.

Your scheme seems to use only 4 values, since you have an

  ASSERT1(komaster >=0 && komaster <=3, 0);

It seems to me that any scheme that uses only 2 bits is 
going to suffer from incomplete information. We'd consider
switching to another scheme but we wouldn't want to do it lightly.
I think we'd have better luck if we could get one more bit for
komaster.

Dan