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Analysis

Why are there two engines?

Stockfish Maia
asks what's best what a human at the levels you pick would play
spends the node budget you set per tier (250k quick, 2M deep by default) one look, no search
gives 1 line quick; on deep as many as you keep (4 by default) 5 moves per level, each with odds
lines? yes never

Every number in that table is a setting: the budgets and lines under Analysis → Engine passes, the levels under Analysis → Maia.

Quick or deep?

Quick runs on import. Deep is the one you ask for, and it jumps the queue. Queue either from a game with Q and D, or over selected rows in Games. A game that has a deep pass is read from it rather than from the quick one.

What did a move cost?

Win% before the move minus win% after it. The default thresholds:

Drop Badge
5 ?! inaccuracy
10 ? mistake
15 ?? blunder

What is left to analyse?

Analysis → Coverage says how much of the library an engine has been over and what finishing it would cost. Backfill quick and Backfill deep queue the rest; a game that already has that tier is skipped. Fill missing levels does the same for Maia. Clear the queue empties it, and Failed runs lists what to retry.

How much work does a pass do?

Analysis → Engine passes sets the node budget of each tier, how many lines a deep pass keeps, and the three thresholds above.

What is Maia asked?

Analysis → Maia sets which human levels are asked, up to five ratings between 1100 and 2000 (a fresh installation asks 2000 only), whether Maia runs on quick passes, deep passes or both, and Ask about both sides: off looks at your moves only, on predicts the opponent's too. It never answers with a line: one look and no search gives a spread of moves, not a continuation. A fill pass adds levels to a game that already has an evaluation.