(;
ST[2]
RU[Japanese]
KM[6.50]
TM[3600]
OT[3x30 byo-yomi]
PW[Albert Yen]
PB[Helcio Alexandre Pacheco]
WR[7d]
BR[3d]
DT[2019-06-02]
EV[WAGC]
RO[2]
PC[Matsue, Shimane, Japan]
WT[USA]
BT[Brazil]
RE[W+Resign]
C[World Amateur Go Championship
White: Albert Yen, 7D
Black: Helcio Alexandre Pacheco, 3D
June 2, 2019, in Matsue, Shimane Prefecture, Japan
Comments by Albert Yen, 7D
Game editors:  Kiren Polara, Myron Souris

Albert Yen's commentary is from his 2nd round win against Brazil's Helcio Alexandre Pacheco.  Albert gives even more variations for his favorite pincer opening.  Although, the game is almost over by move 24, Albert continues the commentary with useful explanations of common shapes and tesujis.  For the game moves, Albert also includes LeelaZero's (AI) winrates.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.  To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.];
B[dp]
C[46.5% (45.9%)
3.1k playouts

Note:  LeelaZero's winrate percentage above is the winning estimation for the player who just moved.  The parenthesized percentage is how much the winning estimation increased (or decreased) as a result of the given move.  The playout count (in this case 3100) indicates the number of Monte Carlo runs in the game tree search - very roughly speaking, the more playouts the better the estimation.

Be warned that the winrates in this game may not be completely accurate, because WAGC uses Japanese rules, which has a 6.5 point komi rather than LeelaZero's 7.5 point komi.  In a normal game this would barely make a difference, but because the margin of lead in this game is very small throughout one point can make a big impact.  In other words, Black's position is always better than what the winrate indicates.];
W[pd]
C[53.6% (0.1%)
1.7k playouts];
B[dd]
C[46.4% (-0.0%)
1.0k playouts];
W[pq]
C[53.6% (0.0%)
1.0k playouts];
B[qo]
C[46.4% (0.0%)
1.1k playouts];
W[pm]
LB[qm:C][on:B][oo:A][op:D]
C[52.9% (-0.7%)
1.0k playouts

This is a move that I've played for a while after AI fuseki became popular.  I use this pincer because very few people know about these josekis (many are very old and not played anymore).  I have achieved good results with this move in this tournament (played this move 4 out of 8 games and won all 4 games)

Traditionally A, B, C are all possible (tenuki is an option, too).  Now with AI people also play at D, which is the most complicated variation. 

I can't explain this in too much detail here but I'll list a few basic variations because this corner decided the outcome of the game.

Conclusion: If you don't know these variations, just tenuki now or after exchanging P5 with O4.  It's never wrong to play that way.]
(;
B[op]
C[45.4% (-1.7%)
1.0k playouts]
(;
W[pp]
C[55.0% (0.4%)
1.0k playouts];
B[po]
C[45.0% (0.0%)
1.1k playouts];
W[oo]
LB[np:A][oq:B]
C[55.0% (0.0%)
1.1k playouts

This is the only move for White.

Usually black plays at A, but AI thinks B is also possible (and maybe even better).]
(;
B[np]
C[45.0% (0.0%)
1.0k playouts

This battle slightly favors White.];
W[on]
C[55.1% (0.1%)
1.0k playouts];
B[rq]
C[44.9% (0.0%)
1.0k playouts];
W[nr]
C[54.1% (-1.0%)
1.0k playouts];
B[lp]
LB[mq:A]
C[44.9% (-1.0%)
1.0k playouts

A is more common but the result is about the same.];
W[rr]
C[55.5% (0.5%)
1.0k playouts]
(;
B[rp]
LB[ro:A]
C[41.1% (-3.3%)
1.0k playouts

This is a slow move.  A is correct (see variation).];
W[qr]
C[56.8% (-2.0%)
1.0k playouts];
B[rm]
C[43.4% (0.2%)
1.0k playouts]
(;
W[rl]
LB[ql:B][qm:A][mq:C]
C[49.5% (-7.1%)
1.0k playouts

At this point it might be better for Black to sacrifice at B.

The fight at A is possible but seems a little dangerous for Black.

Leela suggests that I should play more peacefully at C]
(;
B[rn]
C[30.6% (-19.9%)
1.0k playouts

However, this is much worse than any of the other 2 variations.  Black lived with only 2 eyes in the game and white gained strong influence.  The game is almost over here (white has 75% winrate).];
W[ql]
C[70.2% (0.8%)
1.0k playouts]
(;
B[so]
LB[qm:A]
C[12.6% (-17.2%)
1.0k playouts

This move is incomprehensible.  With A sente black is alive locally and doesn't need to spend another move here.];
W[mq]
C[88.2% (0.9%)
1.0k playouts

White's winrate is at 88% right now, though the game has barely started.];
B[mp]
LB[fc:A][nc:B][qf:D][gq:C]
C[10.7% (-1.1%)
1.0k playouts

Black should think about tenuki here.  Connecting is a bit heavy.

A through D are all possible.];
W[kq]
C[89.4% (0.0%)
1.0k playouts];
B[jo]
C[11.3% (0.7%)
1.0k playouts];
W[ln]
C[88.7% (0.0%)
1.0k playouts

This aims to make Black's shape heavy.]
(;
B[jq]
C[11.6% (0.3%)
1.0k playouts];
W[kp]
C[88.7% (0.3%)
1.0k playouts];
B[ko]
C[11.3% (0.0%)
1.0k playouts]
(;
W[jp]
C[89.1% (0.4%)
1.0k playouts];
B[ip]
C[11.3% (0.4%)
1.0k playouts

Pushing here first before defending m3 cut is an important sequence.];
W[lq]
C[88.3% (-0.4%)
1.0k playouts

Small mistake.  Descending at L2 is better in terms of points.  I played here thinking that Black may have liberty shortage in the center but this 1 liberty doesn't actually change the fight at all.]
(;
B[io]
C[9.9% (-1.7%)
1.0k playouts];
W[lo]
C[89.8% (-0.3%)
1.0k playouts];
B[km]
C[10.4% (0.2%)
1.0k playouts];
W[cq]
LB[lm:A]
C[90.1% (0.5%)
1.0k playouts

Small mistake.  A is a little bigger now.];
B[cp]
C[9.9% (0.0%)
1.0k playouts];
W[dq]
C[90.2% (0.0%)
1.1k playouts];
B[ep]
C[10.3% (0.4%)
1.0k playouts];
W[fr]
C[88.7% (-1.0%)
1.0k playouts];
B[lm]
C[10.8% (-0.5%)
1.0k playouts];
W[mn]
C[89.4% (0.2%)
1.0k playouts]
(;
B[hl]
LB[dh:B][di:A][dj:C]
C[5.9% (-4.6%)
1.0k playouts

Losing move.  This is way too slow.  Black's last chance to win is to play around D11 to develop the left side.];
W[ci]
C[93.4% (-0.6%)
1.0k playouts];
B[cg]
C[6.8% (0.2%)
1.0k playouts]
(;
W[gq]
C[91.0% (-2.2%)
1.0k playouts

This is a favorable exchange for White (eliminates aji at F3), but Black can tenuki and punish White's invasion on the left side.]
(;
B[gp]
C[7.6% (-1.4%)
1.0k playouts

Black was basically tricked here.  This exchange is very good for White.];
W[ei]
C[92.7% (0.3%)
1.0k playouts];
B[gi]
C[6.3% (-1.0%)
1.0k playouts];
W[dl]
C[93.6% (-0.1%)
1.0k playouts

After White settled here Black has no chance of winning.  White has over 30 points in the bottom while Black has close to nothing.  I shut out this game very early.];
B[bl]
C[6.9% (0.5%)
1.0k playouts

Black tries to take away White's base with this move, but this is not big in terms of points.];
W[eg]
C[93.2% (0.2%)
1.0k playouts];
B[ce]
C[6.9% (0.2%)
1.0k playouts];
W[bf]
C[92.8% (-0.3%)
1.0k playouts

Tesuji to fix D12 cut.]
(;
B[bg]
C[7.4% (0.2%)
1.0k playouts];
W[gg]
C[92.9% (0.3%)
1.0k playouts]
(;
B[gd]
LB[dh:A]
C[7.3% (0.2%)
1.0k playouts

After the exchange Black cannot cut at A.];
W[nc]
C[92.9% (0.2%)
1.0k playouts];
B[ih]
C[6.4% (-0.8%)
1.0k playouts];
W[dg]
C[93.0% (-0.6%)
1.0k playouts];
B[cf]
C[7.1% (0.2%)
1.0k playouts];
W[ig]
C[92.2% (-0.6%)
1.0k playouts

No further comments.];
B[jg]
C[7.9% (0.1%)
1.0k playouts];
W[if]
C[92.1% (0.0%)
1.0k playouts];
B[md]
C[7.2% (-0.7%)
1.0k playouts];
W[id]
C[93.3% (0.5%)
1.0k playouts];
B[qd]
C[5.8% (-0.9%)
1.0k playouts];
W[qe]
C[94.3% (0.1%)
1.0k playouts];
B[pe]
C[4.7% (-1.0%)
1.0k playouts];
W[qc]
C[95.7% (0.4%)
1.0k playouts];
B[rd]
C[4.3% (0.0%)
1.1k playouts];
W[re]
C[95.9% (0.3%)
1.0k playouts];
B[rc]
C[4.4% (0.3%)
1.0k playouts];
W[pc]
C[95.6% (0.0%)
1.1k playouts];
B[qb]
C[4.7% (0.3%)
1.0k playouts];
W[pb]
C[95.7% (0.4%)
1.0k playouts];
B[rb]
C[2.9% (-1.3%)
1.0k playouts];
W[qg]
C[97.0% (-0.1%)
1.0k playouts];
B[pf]
C[2.5% (-0.5%)
1.0k playouts];
W[mc]
C[97.5% (0.0%)
1.0k playouts];
B[lc]
C[2.8% (0.3%)
1.0k playouts];
W[ld]
C[97.5% (0.3%)
1.0k playouts];
B[je]
C[2.2% (-0.3%)
1.0k playouts];
W[kc]
C[98.0% (0.2%)
1.0k playouts];
B[ie]
C[2.0% (0.0%)
1.0k playouts];
W[jf]
C[97.9% (-0.1%)
1.0k playouts];
B[kf]
C[1.7% (-0.3%)
1.0k playouts];
W[he]
C[98.4% (0.2%)
1.0k playouts];
B[kd]
C[1.8% (0.3%)
1.0k playouts];
W[le]
C[97.9% (-0.2%)
1.0k playouts];
B[jc]
C[1.3% (-0.7%)
1.0k playouts];
W[lb]
C[98.8% (0.1%)
1.0k playouts];
B[ke]
C[1.3% (0.1%)
1.0k playouts];
W[kg]
C[98.8% (0.1%)
1.0k playouts];
B[hf]
C[1.5% (0.3%)
1.0k playouts];
W[hg]
C[98.8% (0.3%)
1.0k playouts];
B[hd]
C[1.3% (0.1%)
1.0k playouts];
W[lf]
C[98.7% (-0.0%)
1.0k playouts];
B[ge]
C[1.3% (0.0%)
1.0k playouts];
W[jh]
C[98.6% (-0.1%)
8.5k playouts

Black resigns.]
)
    (;
    B[dh];W[di];B[eh];W[fh];B[fi];W[dg];B[ch];W[cf]
    C[The cut doesn't work.]
    )
)
    (;
    B[cf];W[ch]
    LB[bg:A]
    C[A is very big later.]
    )
)
    (;
    B[ck]
    C[Proper move.]
    )
)
    (;
    W[dk]
    C[This is proper for White.]
    )
)
    (;
    B[di];W[kn];B[jm];W[jn];B[in];W[im];B[il];W[hm];B[hl];W[gm];B[gl];W[fm];B[gp]
    C[The cut is not very severe right now.]
    )
)
    (;
    B[lo];W[io]
    C[If Black connects I'll cut.  With K4 exchange I've created a miai of 2 cuts.

Nevertheless, Black should still connect here because this leads to a more complicated game.];
    B[hp];W[in];B[km]
    C[Black will find more opportunities to make a comeback this way.]
    )
)
    (;
    W[kr];B[lo];W[jp];B[io]
    C[If I defend the cut first Black will not block later.]
    )
)
    (;
    B[kp];W[jq]
    C[I want Black to make this exchange.]
    )
)
    (;
    B[qm];W[ol];B[pn]
    C[This sequence is better for Black in every way (more points and weakens white's outside)]
    )
)
    (;
    B[qm];W[ql];B[mr];W[or];B[pl]
    C[Black can fight here.  Although it's complicated this is Black's best move.];
    W[ol];B[pk];W[qj];B[pi]
    C[Fighting will ensue (Note that P9 is sente so this move works).]
    )
)
    (;
    W[mq];B[mp];W[kq];B[ql];W[mn]
    C[White is good here.]
    )
)
    (;
    B[ro];W[qq];B[ql]
    (;
    W[ok];B[pj]
    )
        (;
        W[ln];B[jp];W[ok]
        C[This is still roughly an even fight.]
        )
    )
)
    (;
    B[oq];W[or];B[nr];W[pr];B[on];W[no];B[mp];W[mo];B[lp];W[lo];B[kp];W[ko];B[jp];W[qm]
    LB[rq:A][rr:B][sr:C]
    C[This leads to a very complicated fight that will later involve the ko with black A, white B, and black C.]
    )
)
    (;
    W[oq];B[np];W[mq]
    LB[pm:A]
    C[The pincer at A becomes useless now.  White cannot play this way.]
    )
)
    (;
    B[oo];W[np];B[pk]
    LB[nm:A][rm:B]
    C[A and B are both traditional josekis.]
    (;
    W[nm]
    (;
    B[qm];W[pn];B[qn];W[po];B[qp];W[pp];B[qq]
    C[Old joseki.  AI prefers White.]
    )
        (;
        B[no]
        C[AI recommends this move.];
        W[mp];B[mo];W[lp];B[lo];W[kp];B[qf]
        C[a fighting-oriented game.]
        )
    )
        (;
        W[rm];B[om];W[pn]
        (;
        B[on];W[po];B[op];W[pp];B[oq]
        C[Also old joseki.  Most players (including AI) prefer white.]
        )
            (;
            B[op];W[oq];B[on];W[qp];B[ro];W[po];B[pp];W[qq];B[pl]
            (;
            W[rn];B[rl];W[rp];B[qf]
            LB[rn:A]
            C[About even result (according to AI).  Also an old joseki.

However, A could be a mistake.]
            )
                (;
                W[qm];B[ql];W[rl];B[rk];W[qj];B[qk];W[rp]
                C[AI gives white a favorable winrate in this position (roughly 60%, and initial winrate for white is 53%).

This looks better than the joseki.]
                )
            )
        )
    )
    (;
    B[qm];W[ql];B[pl];W[qk];B[op]
    (;
    W[on];B[oq];W[qn];B[ro];W[rm]
    C[New joseki.  Black will tenuki locally.

Compared with the other joseki where Black tenuki, white is a little stronger than the stone at P6 puts more pressure on black's corner than P7 (where old joseki plays)]
    )
        (;
        W[om];B[oq];W[qn];B[ro];W[rn]
        LB[nc:A][qc:B]
        TR[om]
        C[Black can actually tenuki here.  White can live in the corner later but it's not urgent to fix the aji yet. 

AI thinks Black is slightly better in this joseki.  That's why the triangle move was changed to P6.];
        B[pn];W[rm];B[mq]
        LB[pn:A]
        C[Old joseki.  Now most players (including AI) like White.

However, Black can play better (move A is questionable).]
        )
    )
)

