Re: [gnugo-devel] gnugo 3.4 problems

[bump]

Gunnar wrote:

> > This doesn't address the problem at move 118.
> 
> That problem has already been solved between 3.4 and 3.6 in the sense
> that O15 is now valued lower than the correct semeai moves at S17 and
> T17. Unfortunately S19 is valued even higher, but that's the same
> problem as in move 120.

On my machine, GNU Go still generated 118 at O15 when the game was
replayed using --replay black. When I loaded the game and
generated a move it played S19.

> Move 104, black N8:
> Semeai move is P19, leaving a 3-step ko in black's favor.
> The played move at N8 (tenuki) leaves a 2-step ko in black's favor.
> 
> Move 108, black L10:
> Semeai move is P19, leaving a 2-step ko in black's favor.
> The played move at L10 (tenuki) leaves a direct ko where white still
> must find the first ko threat.
> 
> Move 114, black T15:
> Correct move is P19, leaving a direct ko where white must find the
> first ko threat. 
> The played move at T15 leaves a direct ko where black must find the
> first ko threat.
> Tenuki leaves a 2-step ko in white's favor.

This is all exactly correct. Especially, Move 114 should
not take the ko until the last step of the semeai, which
is of course a general principle.

> Since GNU Go only distinguishes between good ko where the opponent
> must find the first ko threat and bad ko where itself must find the
> first ko threat, it's only at move 114 where it has a chance to tell
> the good moves from the bad moves.

Still this is a very good semeai game. Here's another:

(;GM[1]FF[4]DT[2004-11-20]RU[Japanese]SZ[19]
KM[0.0]
PW[Daniel Bump]
PB[GNU Go 3.7.1 prerelease]
HA[9]AB[dd]AB[jd]AB[pd]AB[dj]AB[jj]AB[pj]AB[dp]AB[jp]AB[pp];
W[qf];B[nd];W[ld];B[gd];W[oc];B[od];W[pc];B[qd];W[mb];B[qc];
W[qb];B[rb];W[pb];B[cg];W[ph];B[pm];W[mg];B[mq];W[qq];B[qp];
W[pr];B[rq];W[rr];B[jh];W[cc];B[dc];W[cd];B[cb];W[bb];B[db];
W[ce];B[ba];W[ab];B[bf];W[be];B[ef];W[cf];B[bg];W[ee];B[ff];
W[de];B[rp];W[fc];B[fb];W[gc];B[gb];W[hc];B[hb];W[ec];B[eb];
W[ic];B[ed];W[fd];B[fe];W[ib];B[bc];W[ad];B[kb];W[ha];B[kd];
W[lc];B[jb];W[he];B[le];W[me];B[md];W[ke];B[lf];W[kf];B[lg];
W[ie];B[nc];W[nb];B[ge];W[je];B[pq];W[ca];B[df];W[ga];B[mh]
)

W made some mistakes in this game but we are concerned
with black's mistakes, not white's.

Black should have killed the upper right corner at 42.

At move 58 if B connects at C19 W can only get a very bad
ko. But the correct local move is A14 which wins the ko
outright.

Move 59 is W's move but this is also a good test. W's
move is wrong, and W should throw in at C19 to get seki.

At move 60 B can get seki at A14 or a favorable ko at
C19.

Dan