I recently finished a go game with GnuGo, and somehow the system turn one of my very alive stone dead, and then declare the entire circled area as non-territory even though it’s my territory.
As the result, I lost the game even though I should have won.
Please review the game again for me as this affect my rank quite a lot when OGS keeps having these miscalculation errors left and right.
This is a well-known problem. Two threads have discussed it. One was closed. One is still open: A compendium of OGS's terrible scoring system confusing beginners. The problem is that the AI interpolates its own judgment rather than scoring the board as it stands. The reason the whole corner is unscored is that the AI thinks the border is not technically closed. You are right that the game should be annulled (game results cannot be reversed). You can file a report from the game tab (click the triangle on the right-hand panel), and a mod will annul it.
I think this blow up of the down right corner explains it all.
As you can see the black stone at T5 is transparent.
If you hover with your mouse over the board , it looks like this.
It seems that Black did hover there, but didn’t click (to place the stone there).
The bot doesn’t see that stone that isn’t there and decides that the right bottom area is still open. And does’t count it as black territory.
I took the final board position of the game that @mimiucute1509 linked in the OP.
So I think the bot assumes that move 147 was not placed there.
Something is wrong with that bot.
It seems like if we defer to kata to determine dead stones, it might make sense to get the score/area map from kata too. Even with that stone dead, the larger group could have lived
With White to play (I guess all bot games are scored this way?) KataGo thinks White can live in the corner. Does it end up as a seki? I’m still not sure how that (gray) stone is supposed to end up dead.
(Of course the autoscore v3 algorithm would get it right, leaving all those stones alive since none of their statuses were ever in question.)