[gnugo-devel] reinstating value(100) owl defense moves?

[Evan Daniel]

Thinking about the owl code, it occurred to me that there could
perhaps be significant gains to be had by reinstating and judicious
use of the special case of value(100) for owl defense moves.  That is,
if an owl defense pattern matches and has value(100), owl_defend
declares victory without further reading.

Clearly, bad patterns here could cause significant problems, so
caution would be needed.  However, I believe the potential gains are
also quite significant.  Currently, for example, owl reads out the
life and death of the tripod group every time it appears in a game. 
It gets it right, and considers all important variations, but it takes
over 400 owl nodes to do it.  That means that there could well be
cases in deep reading where owl would arrive at a knowbly alive tripod
group, but be unable to read it correctly due to depth or node count
limits.  A handful of patterns could at least partially fix this:

|.????
|.????
|.O???
|*.O??
|..O..
|.....
+-----

:8,-,value(100)

This pattern reduces the node count on ld_owl:151 from 435 to 363.  A
few related patterns could easily drop it much further.

After writing a small handful of patterns, I was able to reduce owl
nodes on ld_owl.tst from 22636 to 21420 (~4%); more gains are clearly
possible without much work.

So, before I go spend much more time on this, are there any objections
to the idea?


Evan Daniel