difference in winrate and scorelead between MoveInfos and RootInfo about katago HOT 1 OPEN

Hi cofdam!

This looks like intended behavior. Generally, in MCTS, the winrate or score or any other similar statistic about a node is based on a weighted average of all the moves available at that node, rather than solely that of the believed best move. For example, all else equal, a position in which every reasonable move leads to a 94-95% winrate may more likely to be truly winning than one in which only one move has a 95% winrate, especially if the search is not very deep and the apparent 95% winrate of that one move might be a standalone outlier.

The weighting increasingly concentrates on the believed best move as the node is searched more, and of course the root node has the most search of all, which is why you observe only a tiny difference. When applied throughout the whole search tree, especially at deep nodes without many visits, this overall works better in practice at producing strong play and analysis than weighting only the best move, although in places like the root node and when there are a lot of visits, the difference may not matter much.

There isn't anything to "workaround" here, rather it would be up to you to decide which winrate you wish to use for your purpose. The root winrate is the winrate computed for the root node in the same weighted average manner as all other nodes. The best move winrate is solely the winrate of the best move without averaging other moves at the root... but the best move winrate is still a weighted average of the winrates that could follow after the various opponent replies, rather than just the single best opponent reply, and each of those is a weighted average of the winrates that follow after the possible replies to the opponent reply, rather than only the best reply to the reply and so on.

from katago.