Automatic analysis

Arasan 26.1, the engine included in the app, goes through the main line of a game and gives it back annotated. It is started from the editor, for the open game, with the Automatic analysis button at the bottom of the Engine card or from the Board menu; or from the list, for one or more selected games, with right click → Automatic analysis… or from the Game menu.

Your analyses never overwritten

Terza Torre believes that the analyses you make yourself, perhaps in the heat of the moment right after playing a game, matter far more than any annotation by a chess engine. That is why your comments, your evaluations of a position and the variations you create are never overwritten by the engine’s automatic analysis. The engine keeps its analyses as annotations alongside yours. If it has to overwrite something, it overwrites an old analysis of its own, never yours. You can choose at any moment to hide or show everything the engine annotates, with the switch in the Analysis summary window or the button in the Notation window.

Depth

The deeper it is, the more reliable the verdict and the longer it takes to complete. The moves in the engine’s opening book are looked at only to depth 12, for the graph, without judging them.

Overwrite existing analyses — on, a game already analysed is done again; off, it stays as it is and is skipped.

What it writes into the game

• The evaluation of every move of the main line, which the bar beside the board shows move by move.
• The verdict: ?!, ?, ??, !, !!, □ are the symbols the engine uses to tell you what it thinks of the moves played!
• The best line, as a variation, where there is a mistake.
• A few words on the moments that matter, the most serious first: a mate allowed or missed, the game changing hands, a won position let go, the opponent’s mistake not exploited, material lost, the only move that holds the position.
• The name of the opening, on the last move of theory.
• The accuracy of each of the two players, as a percentage: theory moves count as perfect.
• The engine, the depth and the date, for example “Arasan 26.1 · depth 22 · 25 Oct 2026”.

In the editor these engine annotations are shown only with its button on in the Notation, and they are recognised by the processor sign. Yours stay: comments, symbols, variations, arrows and times are not touched, and a second analysis replaces only what the engine had written. An engine variation that you change becomes yours.

In the list, an icon marks the analysed games, and search finds them with Engine analysis.

From the editor

The analysis locks the window, showing the progress while the engine works. At the end the result is a change like any other: you keep it with Save (⌘S) and undo it with ⌘Z, which during the analysis stops it. During the analysis the live engine turns off, and if it was on it turns back on at the end. On a game without moves the button is off.

The ⓘ next to the button opens the Analysis summary: how the game was decided, the evaluation graph, the accuracy of the two players with their !!, !, ?!, ? and ??, and the engine with depth and date. See The game editor.

From the list

The games are analysed one at a time, in the order of the list, in the background: Background work, at the bottom of the sidebar, says how far it has got. Each game saves itself as soon as it is finished. Stop interrupts: the finished games stay analysed, the one halfway through stays as it was. During an import, the analysis waits for it to finish.

A game open in an editor without changes takes the analysis at once, in its window. One with unsaved changes stays as it is and the report says so; a game changed and saved in the meantime is not overwritten either.

At the end a report says how many games were analysed, skipped or left out for a reason.

Free and Pro

Live analysis, in the editor, is free. Automatic analysis, at every depth, belongs to Pro.