[computer-go] Example for Morphys law in Evaluation

[Magnus Persson]

Quoting Chrilly <c.donninger at wavenet.at>:

>> It is late here in Europe and this post is not very coherent. So here is the
>> point: "Static evaluation of groups in go is very very difficult. 
>> Monte Carlo
>> evaluation was sent from heaven".
>>
> One should always inspect the gifts carefull. Even if the gift  comes 
> from heaven. It can be a Trojan horse.

I see monte carlo evaluation as something that not yet has reached its full
potential.

With static full board evaluation one needs a complete and correct
implementation of all possible situations that are likely to arise on a go
board. If there is limits in the evaluation then I think search will not be
able to compensate for this.

With MC evaluation one can add some simple local knowledge which improves the
evaluation in most situations, and search work quite well in removing those
moves that evaluated too high early in search.

I attach a very nice 9x9 test position (from a real game on CGOS) I have used
during the development of Valkyria as an example of what MC-eval + a litlle
knowledge can do. White plays first and should try to live but Black has some
really nice tesujis to keep white from living but white can connect all stones
and win. There is also a very nice sequence where black kills white if white
makes the obvious response.

The nice thing about this position is that black can keep attacking 
white to for
about 11 ply which Valkyria now can see in a few minutes with very selective
UCT-search.

When I started working on Valkyria it would sometimes not even get the first
move right in 10 minutes of thinking time, but with some basic go knowledge it
now can go very deep. I think this positions is special in the sense that it
can be searched very deep quickly, but the forcing moves that has to 
played for
the first 6-7 ply are not trivial.

If your static evaluation is good then you might not need to search 
deeper than
6-7 ply to see that white is alive or connected, but if the evaluation makes
errors then this might be really hard for traditional full board search.

-MP

-------------- next part --------------
(;GM[1]FF[4]SZ[9]AP[SmartGo:1.4]
PW[b]
PB[w]
KM[0.5]
;B[ge];W[eh];B[ee];W[dd];B[de];W[ce];B[cf];W[bf];B[cd];W[be];B[fe];W[cc]
;B[bg];W[bd];B[cg];W[ec];B[df];W[hc];B[gc];W[gb];B[hd];W[fc];B[gd];W[ag]
;B[hb];W[bh];B[ch];W[ci];B[di];W[gh];B[ic];W[hi];B[hg];W[hh];B[fh];W[fg]
;B[fi])