[gnugo-devel] Owl hashing broken in trevor:261

[Trevor Morris]

This discussion relates to trevor:261.

In short, by disabling owl hashing, confirm_safety works correctly.
Be enabling the owl hashing (default), there is a problem.  Simplest
solution would be to clear the cache before checking move safety,
but that seems like a cop-out.  Any thoughts on why this is happening?

FYI (in case you don't remember):
 HASH_OWL_ATTACK   0x0100
 HASH_OWL_DEFEND   0x0200

The following commands all incorrectly find a blunder:
gq  -l games/trevor/trevor_26.sgf -L 39 -t
gq  -l games/trevor/trevor_26.sgf -L 39 -t --hash 0x0221
gq  -l games/trevor/trevor_26.sgf -L 39 -t --hash 0x0121
....
Top moves:
1. F9  16.23
2. A2  8.28
3. A3  0.37
Checking safety of a black move at F9
Move at F9 would be a blunder.
Checking safety of a black move at A2
Move generation likes A2 with value 8.28
genmove() recommends A2 with value 8.28
black (X) move A2


Completely disabling Owl hashing solves the problem:
gq  -l games/trevor/trevor_26.sgf -L 39 -t --hash 0x0021
Top moves:
1. F9  16.22
2. A2  8.28
3. A3  0.36
Checking safety of a black move at F9
Move generation likes F9 with value 16.22
genmove() recommends F9 with value 16.22
black (X) move F9


-Trevor