Positional Superko violation: KataGo allows move that repeats board position (identical hash)

[dany52]

Expected: B19 at move 3 is forbidden. Actual: KataGo allows it despite identical board hash.

(;SZ[19]PL[B]AB[aj][bj][cj][dj][ek][ej][fl][fj][gm][gk][gj][hq][hp][ho][hn][hm][hl][hk][jq][jp][jo][jn][jm][jl][jk][jj][ji][jh][jg][jf][je][jd][jc][jb][lr][mr][mq][mp][mo][mn][mm][ml][mk][mj][mi][mh][mg][mf][me][md][mc][mb][nr][or][pr][pq][pp][po][pn][pm][pl][pk][pj][pi][ph][pg][pf][pe][pd][pc][pb][qr][rr][sr][sq][sp][so][sn][sm][sl][sk][sj][si][sh][sg][sf][se][sd][sc][sb][sa][hr][hs][kr][jr][ba][cb][db][da][ja]AW[lk][li][nk][ni][ok][oi][og][qm][qk][qi][qg][rm][rk][ri][rg][ak][bk][ck][dk][al][cl][el][bm][dm][fm][an][cn][en][gn][go][gp][gq][gr][gs][fs][bs][ar][bq][cr][ds][er][dq][cp][bo][ap][do][ep][fq][fo][ss][rs][qs][ps][os][ns][ms][ls][ks][js][is][ir][iq][ip][io][in][im][il][ik][ij][ii][ih][ig][if][ie][id][ic][ib][ka][la][ma][na][oa][pa][qa][ra][rc][qc][qe][re][rq][rp][ro][qo][qp][qq][oc][nc][ne][oe][ng][nm][om][oo][no][nq][oq][kq][lq][ko][lo][lm][km][kk][ki][lg][kg][ke][le][lc][kc][ac][ab][ad][ae][af][ag][ah][ai][hj][hi][gi][fi][ei][di][ci][bi][bh][dh][ch][cg][dg][bg][bf][cf][df][ef][ff][gf][hf][hg][gg][gh][hh][fh][fg][eg][eh][bb][bc][bd][be][ce][cd][cc][dc][dd][de][ec][eb][ed][ee][fd][fe][fc][fa][ia][ha][ga][gb][fb][gc][hd][hc][hb][gd][ge][he]AE[br][aq][as][cq][bp][co][dp][eq][fp][eo][dn][aa][ca]AP[Sabaki:0.52.2]CA[UTF-8])

 ./katago-1.16.3.sh 
KataGo v1.16.3
Using Chinese-OGS rules initially, unless GTP/GUI overrides this
Initializing board with boardXSize 19 boardYSize 19
Loaded config /home/dany/baduk/katago-v1.14.1-cpu-avx2/default_gtp.cfg
Loaded model /home/dany/baduk/nets/kata1-b18c384nbt-s834.bin.gz
Model name: kata1-b18c384nbt-s8341979392-d3881113763
GTP ready, beginning main protocol loop
kata-get-rules
= {"friendlyPassOk":true,"hasButton":false,"ko":"POSITIONAL","scoring":"AREA","suicide":false,"tax":"NONE","whiteHandicapBonus":"N"}

loadsgf chinese-beast.sgf
Sgf has no rules or komi, using default rules: koPOSITIONALscoreAREAtaxNONEsui0whbNfpok1komi7.5
= 

showboard
= MoveNum: 0 HASH: FF6DAFE8A195A821F05CE1819119B3E6
   A B C D E F G H J K L M N O P Q R S T
19 . X . X . O O O O X O O O O O O O O X
18 O O X X O O O O O X . . X . . X . . X
17 O O O O O O O O O X O O X O O X O O X
16 O O O O O O O O O X . . X . . X . . X
15 O O O O O O O O O X O O X O O X O O X
14 O O O O O O O O O X . . X . . X . . X
13 O O O O O O O O O X O O X O O X O O X
12 O O O O O O O O O X . . X . . X . . X
11 O O O O O O O O O X O O X O O X O O X
10 X X X X X X X O O X . . X . . X . . X
 9 O O O O X . X X O X O O X O O X O O X
 8 O . O . O X . X O X . . X . . X . . X
 7 . O . O . O X X O X O O X O O X O O X
 6 O . O . O . O X O X . . X . . X . . X
 5 . O . O . O O X O X O O X O O X O O X
 4 O . O . O . O X O X . . X . . X O O X
 3 . O . O . O O X O X O O X O O X O O X
 2 O . O . O . O X O X X X X X X X X X X
 1 . O . O . O O X O O O O O O O O O O O
Next player: Black
Rules: {"friendlyPassOk":true,"hasButton":false,"ko":"POSITIONAL","komi":7.5,"scoring":"AREA","suicide":false,"tax":"NONE","whiteHandicapBonus":"N"}
B stones captured: 0
W stones captured: 0

play B A19
= 

showboard
= MoveNum: 1 HASH: 70CF6DF35C9648E80A79EEF2EC48B5CF
   A B C D E F G H J K L M N O P Q R S T
19 X1X . X . O O O O X O O O O O O O O X
18 O O X X O O O O O X . . X . . X . . X
17 O O O O O O O O O X O O X O O X O O X
16 O O O O O O O O O X . . X . . X . . X
15 O O O O O O O O O X O O X O O X O O X
14 O O O O O O O O O X . . X . . X . . X
13 O O O O O O O O O X O O X O O X O O X
12 O O O O O O O O O X . . X . . X . . X
11 O O O O O O O O O X O O X O O X O O X
10 X X X X X X X O O X . . X . . X . . X
 9 O O O O X . X X O X O O X O O X O O X
 8 O . O . O X . X O X . . X . . X . . X
 7 . O . O . O X X O X O O X O O X O O X
 6 O . O . O . O X O X . . X . . X . . X
 5 . O . O . O O X O X O O X O O X O O X
 4 O . O . O . O X O X . . X . . X O O X
 3 . O . O . O O X O X O O X O O X O O X
 2 O . O . O . O X O X X X X X X X X X X
 1 . O . O . O O X O O O O O O O O O O O
Next player: White
Rules: {"friendlyPassOk":true,"hasButton":false,"ko":"POSITIONAL","komi":7.5,"scoring":"AREA","suicide":false,"tax":"NONE","whiteHandicapBonus":"N"}
B stones captured: 0
W stones captured: 0

play W C19
= 

showboard
= MoveNum: 2 HASH: 3C0DA50E3B4771FC80F806C8354FC6F5
   A B C D E F G H J K L M N O P Q R S T
19 .1. O2X . O O O O X O O O O O O O O X
18 O O X X O O O O O X . . X . . X . . X
17 O O O O O O O O O X O O X O O X O O X
16 O O O O O O O O O X . . X . . X . . X
15 O O O O O O O O O X O O X O O X O O X
14 O O O O O O O O O X . . X . . X . . X
13 O O O O O O O O O X O O X O O X O O X
12 O O O O O O O O O X . . X . . X . . X
11 O O O O O O O O O X O O X O O X O O X
10 X X X X X X X O O X . . X . . X . . X
 9 O O O O X . X X O X O O X O O X O O X
 8 O . O . O X . X O X . . X . . X . . X
 7 . O . O . O X X O X O O X O O X O O X
 6 O . O . O . O X O X . . X . . X . . X
 5 . O . O . O O X O X O O X O O X O O X
 4 O . O . O . O X O X . . X . . X O O X
 3 . O . O . O O X O X O O X O O X O O X
 2 O . O . O . O X O X X X X X X X X X X
 1 . O . O . O O X O O O O O O O O O O O
Next player: Black
Rules: {"friendlyPassOk":true,"hasButton":false,"ko":"POSITIONAL","komi":7.5,"scoring":"AREA","suicide":false,"tax":"NONE","whiteHandicapBonus":"N"}
B stones captured: 2
W stones captured: 0

play B B19
= 

showboard
= MoveNum: 3 HASH: FF6DAFE8A195A821F05CE1819119B3E6
   A B C D E F G H J K L M N O P Q R S T
19 .1X3.2X . O O O O X O O O O O O O O X
18 O O X X O O O O O X . . X . . X . . X
17 O O O O O O O O O X O O X O O X O O X
16 O O O O O O O O O X . . X . . X . . X
15 O O O O O O O O O X O O X O O X O O X
14 O O O O O O O O O X . . X . . X . . X
13 O O O O O O O O O X O O X O O X O O X
12 O O O O O O O O O X . . X . . X . . X
11 O O O O O O O O O X O O X O O X O O X
10 X X X X X X X O O X . . X . . X . . X
 9 O O O O X . X X O X O O X O O X O O X
 8 O . O . O X . X O X . . X . . X . . X
 7 . O . O . O X X O X O O X O O X O O X
 6 O . O . O . O X O X . . X . . X . . X
 5 . O . O . O O X O X O O X O O X O O X
 4 O . O . O . O X O X . . X . . X O O X
 3 . O . O . O O X O X O O X O O X O O X
 2 O . O . O . O X O X X X X X X X X X X
 1 . O . O . O O X O O O O O O O O O O O
Next player: White
Rules: {"friendlyPassOk":true,"hasButton":false,"ko":"POSITIONAL","komi":7.5,"scoring":"AREA","suicide":false,"tax":"NONE","whiteHandicapBonus":"N"}
B stones captured: 2
W stones captured: 1

[lightvector]

Not a bug. KataGo deliberately tolerates moves that violate the rules if the GTP controller asks it to make the move, because in practice there are many GTP controllers that don't know how to handle it and/or are very simply coded to forward moves from SGF files that may or may not follow superko.

KataGo will always obey the rules when generating moves, however.