[gnugo-devel] Uncertain defense certainly bad

[bump]

At the end of this message is a game where an uncertain owl defense is
certainly bad.

At move 104, GNU Go 3.3.22 plays a terrible move at R11.
Not only is this worth -1 point with gote but it actually hurts
W's eyeshape. After this move, a full eye becomes a half eye.

The move is contributed by the pattern:

Pattern D123
# tm New Pattern (3.1.17)
# tm Modified (3.1.18)

??*??   expand eye shape, not in corner
?O.O?
?...?
-----

:|,-,value(65)

One possibility here is to make this pattern more
specific. Consider:

??*??   expand eye shape, not in corner
XO.OX
?...?
-----

Assuming the X stones are not dead, the move at * does
not contribute a half eye on the edge. The pattern
could be split as follows:

Pattern D123a

??*??   expand eye shape, not in corner
oO.O?
?...?
-----

:8,-,value(65)

Pattern D123b

??*??   expand eye shape, not in corner
XO.O?
?...?
-----

:8,-,value(65)

??*??   expand eye shape, not in corner
AO.O?
?...?
-----

; attack(A)

This helps a little in the present situation. W still makes a small
defensive move but at least it is not a harmful one.

Dan

(;GM[1]FF[3]
RU[Japanese]SZ[19]HA[0]KM[5.5]
PW[GNU Go 3.3.22]
PB[GNU Go 3.2]
DT[2003-07-01]
SY[Cgoban 1.9.12]TM[-];B[pd];W[dp];B[pq];W[ec];B[qo];W[pf];B[nd];W[qd]
;B[qc];W[qe];B[rc];W[qj];B[jc];W[cd];B[fq];W[cj];B[jq];W[cn];B[dr];
W[cq];B[fo];W[fm];B[hd];W[ff];B[hm];W[pl];B[gk];W[nm];B[gj];W[fh];
B[gn];W[lm];B[mq];W[cr];B[nf];W[nh];B[og];W[lh];B[oh];W[lf];B[qg];
W[ld];B[lc];W[er];B[mc];W[fr];B[ik];W[rh];B[rg];W[qh];B[pg];W[lo];
B[ej];W[di];B[el];W[em];B[dl];W[bl];B[rl];W[ql];B[rm];W[kk];B[oi];
W[np];B[nq];W[in];B[rk];W[qk];B[kd];W[rj];B[nk];W[nj];B[ni];W[oj];
B[mi];W[hb];B[ib];W[hc];B[gd];W[ic];B[ed];W[dc];B[de];W[id];B[hf];
W[ig];B[jb];W[if];B[ha];W[ga];B[ia];W[hi];B[jj];W[pi];B[gb];W[gc];
B[fb];W[fc];B[eb];W[db];B[da];W[ca];B[fa];W[qi];B[hn];W[gq];B[ii];
W[hj];B[jm];W[ih];B[li];W[fd];B[eq];W[eo];B[gp];W[hq];B[mp];W[dq];
B[mo];W[mn];B[no];W[jn];B[jk];W[ke];B[kl];W[mk];B[ll];W[lk];B[ml];
W[nl];B[kh];W[si];B[mh];W[jr];B[kq];W[ir];B[kr];W[jd];B[kc];W[ks];
B[ls];W[js];B[lr];W[fp];B[ji];W[sg];B[rf];W[lg];B[sf];W[gi];B[mj];
W[ok];B[on];W[fl];B[hk];W[fk];B[fj];W[ek];B[fn];W[dj];B[hp];W[me];
B[io];W[km];B[iq];W[hr];B[im];W[jo];B[md];W[le];B[en];W[dn];B[mg];
W[om];B[qm];W[pm];B[pn];W[kg];B[jh];W[jg];B[lp];W[kp];B[jp];W[ko];
B[kj];W[gl];B[hl];W[ne];B[oe];W[sk];B[sl];W[ei];B[sj];W[sh];B[sk];
W[nn];B[fi];W[nk];B[lj];W[mf];B[ph];W[mm];B[jl];W[ij];B[gm];W[ea];
B[ga];W[da];B[tt];W[tt]
)