On Nov 13, 2007 4:05 PM, Jason House <[EMAIL PROTECTED]> wrote: > > > > On Nov 13, 2007 3:57 PM, Petr Baudis <[EMAIL PROTECTED]> wrote: > > > > On Tue, Nov 13, 2007 at 03:32:03PM -0500, John Tromp wrote: > > > On Nov 13, 2007 2:48 PM, Petr Baudis <[EMAIL PROTECTED]> wrote: > > > > > > > I'm now somewhat torn. The speedup from using pseudo-liberty counts > > > > could be huge, estimating from my profiling. On the other hand, it > would > > > > be very useful to still be able to quickly check if a group is in > atari > > > > - it looks like if atari stones would get special attention during the > > > > random games, that could make the bot a lot stronger. > > > > > > > > Is there any known way to get the best of the both worlds? :-) > > > > > > Yes, you can generalize pseudoliberties by extending them > > > with another field, such that if the (summed) pseudoliberty field > > > is between 1 and 4, then the other (summed) field will tell you if all > these > > > are coming from a single true liberty. > > > > Wow, that's great idea! I was trying to think along these lines but > > realized the implementation only after reading what you wrote. > > > > I guess you mean something in the spirit of: > > > > group.xyzzy = 0 > > > > add_liberty(group, coord) > > group.xyzzy += as_int(coord) > > > > remove_liberty(group, coord) > > group.xyzzy -= as_int(coord) > > > > in_atari(group) > > group.pseudlibs <= 4 && is_liberty(group, as_coord( > group.xyzzy)) > > You're right, that would work. > > PS: I think that last one should be: > group.pseudlibs <= 4 && is_liberty(group, > as_coord(group.xyzzy/group.pseudlibs))
I definitely understand the idea now, and it looks very good. However this implementation could break: Say we have pseudoliberties at intersections: 99,100,101. We sum those up to get 300, divide by the number of pseudoliberties - 3, get back 100, check to see if 100 is a liberty, and since it is we conclude that we have one liberty at intersection 100 that we counted three times, and hence our string is in atari. _______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
