Fedya wrote:
Bill: You suggested peeping on

. To me, that looks like the sort of move where, if I played it, I would get criticized for playing aji keshi. Indeed, I thought of that in your comment on move 103 up in the top left for strengthening White needlessly.
Is there any good way to figure out which such moves are aji keshi and which aren't short of having really good reading?
Well, there isn't any one way. I am attaching an edited SGF file with a couple of comments. Go to move 27 and also to move 104,
A knowledge of shape can help. Empty triangles figure into the question of

.
The main question of aji keshi has to do with alternate plays that you give up. A variation for

shows the main play that is given up. It's not a good play. In this case the peep can be called a no loss kikashi, for the reason.
Also, in general, when attacking it is a good idea to peep at the group you are attacking. Usually the connection will make those stone heavy, that is, too big to sacrifice easily. Often, as in this case, the peep will let you move your attack further ahead than otherwise, and strengthen your attacking group.
Quote:
(And I'm not certain why Leela wouldn't want me to kill the White group around C6.)
Because they read the whole board, today's bots can be weak at local reading, including ladders, semeai, and life and death. And Leela-11 is not all that strong, anyway. Bots do not incorporate knowledge like humans do. The sagari to the second line is something that humans learn, but does not occur that often in real games, so a bot might not learn it quickly by self play. So we do not know if Leela actually considered that tesuji, or the sequence shown by Joaz. Letting White live gives Black a good game, so Leela may have had no reason to search locally for a kill. I learned that tesuji when I was around your strength, so I saw it immediately.
(;SZ[19]FF[4]AP[GOWrite:3.0.15]CA[UTF-8]GM[1]ST[3]GN[ ]RU[Japanese]OT[5x30 byo-yomi]PB[Fedya]WR[6k]BR[6k]DT[2019-01-12]FG[259:]KM[6.50]TM[1500]PW[kmaster]RE[W+Resign]PM[2]PC[The KGS Go Server at http://www.gokgs.com/]
;BL[1496.644]B[pd]C[kmaster [6k]: hiFedya [6k]: Hello!]
;WL[1496.61]W[dd]
;BL[1490.391]C[I've been playing the diagonal fuseki any time my opponent gives me the chance in order to make it harder for my opponent to get a large moyo. (And by the same token, as white I've been approaching with White 4 rather than play in the empty corner for the same reason.)]B[dp]
;WL[1493.229]W[pp]
;BL[1467.47]B[qn]
;WL[1484.094]W[ql]
;BL[1447.977]B[on]
;WL[1481.601]W[np]
;BL[1444.699]B[pk]
;WL[1478.284]W[qk]
;BL[1442.544]B[pj]
;WL[1476.152]W[pl]
;BL[1436.548]B[ol]
;WL[1474.274]W[qj]
;BL[1423.054]B[pi]
;WL[1471.095]W[qh]
;BL[1410.082]B[og]
;WL[1466.625]W[qf]
;BL[1391.381]C[I played this to try to secure the corner.Leela wants me to give up the corner and play either M3/M4, or Q14 and try to get something from the resulting thickness.
***Right. This play is defensive. The M-03 approach would attack White's group in the bottom right. Remember, attacking is one main way to make use of thickness.]B[qd]
;WL[1463.102]W[nc]
;BL[1375.243]C[I didn't know what to play here. Leela spent most of its time on this move.]B[lc]
;WL[1457.542]W[ne]
(
;BL[1336.258]C[*** Questionable. The general rule is not to attach to stones you are attacking. See variation.]B[oe]
;WL[1449.901]C[*** White gets to strengthen himself.]W[nf]
;BL[1329.331]C[ ]B[of]
(
;WL[1447.629]C[*** See variation for Black's threat on the right side.]W[pb]
(
;BL[1286.3]C[*** See variation.
See second variation, as well.]B[le]
;WL[1435.237]W[md]
;BL[1283.155]B[ld]
;WL[1430.935]W[mb]
(
;BL[1279.037]C[*** Not bad. See variation.]B[hd]
;WL[1426.443]W[fc]
;BL[1259.308]C[*** Bravo!]B[lq]
;WL[1421.14]W[cn]
(
;BL[1231.479]C[This is where things really start to go wrong. I guess I should have given up the left side in exchange for the bottom and hope I end up with more territory.
*** The game is getting a bit complicated, but that does not make this a bad play. See variations.]B[cl]
;WL[1418.297]W[en]
;BL[1221.349]B[fp]
;WL[1413.271]W[jq]
;BL[1210.793]C[If I had to to it again, I'd play M5 and make it easier to connect to the other Black stones on the right.
*** N-05 is also something to consider.]B[kp]
;WL[1409.601]W[hq]
(
;BL[1202.211]C[*** Problematic. See variations.]B[bp]
;WL[1405.316]C[Now I begin to get in serious trouble.]W[cq]
;BL[1191.165]B[cp]
;WL[1402.211]W[eq]
(
;BL[1181.829]C[I didn't like this, but I liked th ealternative at E4 even less. This way I should be able to capture and live in the corner; if I play E4, where am I going to get eyes?
*** Courage, mon vieux! You are attacking, remember? You have to keep White separated. Hell or high water. See variations.]B[dq]
;WL[1398.931]W[ep]
(
;BL[1174.139]C[This way I can split at either D6 or E5 next.
*** Yeah, but White's connection at E-05 is too good. White can afford to sacrifice a stone or two. See variation.]B[do]
;WL[1392.148]C[*** Not good.]W[dn]
;BL[1172.834]B[eo]
;WL[1388.803]W[fq]
;BL[1169.335]B[fn]
;WL[1386.165]W[fm]
;BL[1156.614]C[Attack!
*** Bravo!]B[em]
;WL[1383.877]W[gn]
;BL[1154.739]B[fo]
;WL[1379.623]W[dm]
;BL[1153.942]B[el]
;WL[1376.932]W[dl]
;BL[1151.303]B[dk]
;WL[1370.876]W[ek]
;BL[1150.638]B[fl]
;WL[1368.114]W[ck]
;BL[1136.351]B[dj]
;WL[1365.088]W[cj]
;BL[1127.366]B[bl]
;WL[1354.344]W[bm]
(
;BL[1085.265]C[*** See variation.]B[ci]
;WL[1351.202]W[di]
;BL[1084.357]B[ej]
;WL[1349.589]W[bi]
;BL[1080.663]B[ch]
;WL[1334.203]C[My attack failed, as I have no way to kill on the left side.
*** Well, you missed the tesuji. Live and learn. However, confining White is not a bad result. See variation for next.]W[bk]
(
;BL[1041.617]B[gm]
;WL[1330.161]W[bh]
;BL[1035.635]C[*** Letting B-12 become double sente was not good.]B[cg]
;WL[1319.03]W[gp]
(
;BL[1013.686]C[I realized the only way I'd win is to get a bunch of territory in the center. However, this and N13 are miai. White's going to be able to destroy my center.
*** This may be OK, but the fight on the bottom side looks kind of urgent. See variation.]B[fe]
;WL[1307.722]W[mg]
;BL[999.973]B[kg]
;WL[1301.93]W[in]
;BL[960.145]B[il]
;WL[1297.644]C[Oh, and now I have to worry about the M3 group.
*** You took your eye off the ball earlier.]W[kn]
;BL[917.411]B[mo]
;WL[1291.683]W[df]
;BL[912.975]B[eh]
;WL[1288.366]W[ff]
;BL[910.14]B[gf]
;WL[1285.201]C[I didn't see this move at all, only E14 or E15. Can't help but think about toothpaste.]W[fg]
;BL[890.201]B[ee]
;WL[1281.442]W[dg]
;BL[882.521]B[de]
;WL[1275.984]W[dh]
(
;BL[881.086]C[*** See variation.]B[cf]
;WL[1273.532]W[ce]
;BL[824.617]C[I figured the only way I could win was to try to kill the D16/F17 stones and get a whole bunth of territory at the top.]B[cd]
;WL[1270.525]W[be]
(
;BL[820.826]C[*** See variation.]B[cc]
;WL[1262.972]W[dc]
;BL[817.665]B[db]
;WL[1249.516]W[ec]
;BL[815.16]B[bd]
;WL[1245.996]W[bf]
(
;BL[813.541]C[*** Strengthens White needlessly. See variation.]B[eb]
;WL[1243.996]C[*** This stone makes it easier to jump to the right and to make eye shape than if it were not here.]W[fb]
;BL[812.366]B[bb]
;WL[1240.043]W[ib]
;BL[806.329]C[*** Bravely done. Attacks both groups.]B[lb]
;WL[1235.205]W[jd]
;BL[786.768]B[if]
;WL[1231.293]W[jf]
;BL[781.496]B[jg]
;WL[1223.609]W[kf]
;BL[775.138]B[lf]
;WL[1221.697]W[ie]
(
;BL[761.473]C[*** Nice try. But see variation.
End of comments.]B[je]
;WL[1210.97]W[hf]
;BL[743.13]B[ig]
;WL[1207.336]W[he]
;BL[734.473]B[hg]
;WL[1190.159]C[And now I'm not going to kill those stones. I probably could have resigned here, but I played on for another several moves.]W[ge]
;BL[731.96]B[gg]
;WL[1159.186]W[fh]
;BL[723.09]B[gd]
;WL[1156.145]W[id]
;BL[721.554]B[fd]
;WL[1150.205]W[hc]
;BL[665.201]B[kd]
;WL[1143.713]W[jc]
;BL[652.424]B[gb]
;WL[1115.287]W[gc]
;BL[650.03]B[fa]
;WL[1112.216]W[ea]
;BL[646.157]B[da]
;WL[1107.631]C[kmaster [6k]: thxFedya [6k]: Thank you for the game]W[hb]
)
(
;B[he];W[gd];B[ge];W[hc];B[jc];W[ic];B[id];W[kc];B[kb];W[jb];B[je]
;C[*** White lives here. But see continuation.]W[gb]
;B[qb];W[pc];B[qc];W[od]
;C[*** Where is White's second eye?]B[ob]
)
)
(
;C[*** Black is alive.]B[bb]
)
)
(
;B[bd];W[bf];B[dc]
)
)
(
;B[ce];W[cf];B[cc]
)
)
(
;C[*** Makes a kind of base for Black, undercuts White.]B[nr]
)
)
(
;B[bh];W[aj]
;C[*** Black has a very nice wall, and White still has problems.]B[fk]
)
)
(
;C[*** Tesuji.]B[bn]
;W[bo];B[an];W[am];B[co];W[ao];B[bn];W[an];B[cm]
(
;W[bn]
;C[*** Oops!]B[ap]
)
(
;W[bk]
;C[*** Oops!]B[bn]
)
)
)
(
;C[*** Hell or high water.]B[eo]
(
;W[do];B[fo];W[fq]
;C[*** A complicated fight, but Black is OK.]B[ho]
)
(
;W[fo];B[do]
(
;C[*** Mistake.]W[dn]
;B[fq];W[er]
;C[*** Oops!]B[fr]
)
(
;W[er];B[hp];W[iq];B[fn];W[go];B[gn];W[ho];B[hn];W[io]
;C[*** One possibility.]B[em]
)
)
)
)
(
;B[ep];W[fq]
(
;B[gq];W[gp];B[gr];W[hr];B[go];W[hp];B[dq];W[fr];B[er];W[gs];B[fn]
)
(
;B[gp];W[dq];B[dm];W[dn]
;C[*** Now White has to worry about making eyes.]B[gn]
)
)
)
(
;C[*** Splits Whites groups apart. Divide and conquer!]B[go]
)
(
;C[*** Undercuts White and threatens, among other things, B-04.]B[gr]
)
(
;C[*** Too passive in this particular situation, I think, but this play prepares to attack both sides. Worth remembering.]B[cq]
)
)
(
;C[*** Threatens the White corner.]B[mo]
)
(
;C[*** Continues the attack.]B[oq]
)
)
(
;C[*** Probably OK, as well. Check with Leela.]B[lq]
)
)
(
;C[*** Peep first.]B[md]
;W[nd]
;C[*** The peep has allowed Black to get further ahead that the one space jump. Also, see continuation.]B[lf]
;C[*** If White plays here, threatening to cut, White has made an empty triangle.]W[od]
)
(
;C[*** Instead of peeping, suppose Black plays the wedge.]B[nd]
;W[md]
;C[*** Now Black has made an empty triangle.]B[od]
;C[*** Also, this connection weakens the Black stone on M-17. Yes, Black has a cutting point at N-15, but White can easily throw away two stones.]W[mc]
)
)
(
;B[rg]
(
;C[*** Mistake.]W[qg]
;B[qi];W[ri];B[rh];W[sj];B[rf];W[re];B[qe];W[sh]
;C[*** And White is still not alive.]B[rd]
)
(
;W[rh];B[rf]
)
)
)
(
;B[pf]
)
)