A solver that admits when it doesn’t know

Klondike solitaire where every deal in Guaranteed mode comes from a set a solver has already played through to a win with Standard scoring, in both Draw 1 and Draw 3. “Winnable” here means winnable if you could see every face-down card, because that’s what the solver sees. The coach tells you when a deal can’t be won, and the hint tells you how sure it is. It’s on the App Store and Google Play; the app page has more.

• Search under a time limit, without lying.The solver gives one of three answers. Winnable: it found a full solution with every card visible. Unwinnable: it exhausted the search and found no win. Unknown: the time or node budget ran out first, and that isn’t a claim either way.
• The honesty reaches the player.When the hint can’t prove a winning line in time, it falls back to a safe move picked by rule and says it’s a guess. The coach tells you whether a deal can still be won. When it can’t tell, it says that too.
• Fast enough to search.Generating legal moves dominated the search, so I rewrote it from generate-then-test to direct generation. Measured on positions from real play, the new version is 2.4 times faster. A differential test pins the new version to the old one’s behaviour.

This is what I want from any AI or automation that touches your business. It should tell you how sure it is, and say “I don’t know” rather than hand you a confident wrong answer. I build for that from the start.

Related: AI and automation for Columbus businesses.