Technology, online play, and variants
Engines and analysis
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Chess engine
A program that analyzes a position, compares legal move sequences, and recommends options based on its calculations.
Graphical User Interface
A visual application that lets users control chess software through a board, controls, and panels instead of text commands.
Local engine
A chess-analysis program that runs on the user's own device and uses that machine's processor and memory.
Cloud engine
A chess-analysis program that performs its calculations on a remote computer and returns the results over a network.
Principal variation
The move sequence a chess-analysis program currently considers the best continuation for both sides from a position.
MultiPV
Level: IntermediateAn analysis mode that displays several candidate moves with a line and evaluation for each one.
Depth
An indicator of how far a chess engine's current search has progressed from the position being analyzed.
Nodes per second
A measure of how many positions a chess engine processes per second during search.
Pondering
Level: IntermediateA mode in which an engine searches while the opponent's clock runs, usually from a predicted reply.
Bitboard
Level: IntermediateA representation with 64 zero-or-one indicators, one per square, marking which squares belong to a chosen set.
Evaluation function
Level: IntermediateA procedure that assigns a numerical estimate to a position so a chess program can guide its search.
NNUE
A neural-network architecture designed to evaluate chess positions while updating efficiently between nearby positions.
Minimax
Level: IntermediateAn algorithm that chooses a move while assuming both sides will always make their best available decisions.
Alpha-beta pruning
Level: AdvancedA method that skips branches unable to change the final choice when both sides seek their best result.
Iterative deepening
Level: AdvancedA strategy that repeats search with increasing limits so a completed result is always available.
Move ordering
Level: AdvancedA technique that chooses which moves to search first so unhelpful branches can be rejected sooner.
Principal variation search
Level: AdvancedAn optimization that fully searches the first candidate and initially tests later moves with a narrower check.
Late move reductions
Level: AdvancedA technique that initially searches moves placed late in a position's analysis order at reduced depth.
Null-move pruning
Level: AdvancedA heuristic that tests a fictional pass to discard positions that appear clearly sufficient.
Quiescence search
Level: AdvancedAn extension that continues selected tactical moves until the position is stable enough to evaluate.
Horizon effect
Level: IntermediateAn error caused when a decisive consequence lies just beyond the search limit and distorts the evaluation.
Monte Carlo tree search
Level: AdvancedA method that repeatedly explores variations and spends more analysis on moves that appear promising.
Static exchange evaluation
Level: AdvancedA fast calculation that estimates the material balance of successive captures and recaptures on one square.
Transposition table
Memory that lets a chess engine reuse results for positions it has already searched.
Zobrist hashing
Level: AdvancedA method that creates a quickly updatable numerical fingerprint for the complete state of a chess position.
Perft
Level: IntermediateA test that counts every legal move sequence to an exact search depth.
Opening book
A database of opening positions and moves that a chess program can consult before normal search.
Tablebase
A precomputed database that gives exact results for endgames within a limited number of pieces.
Endgame bitbase
Level: AdvancedA compact precomputed structure that stores minimal outcome information for many endgame positions.
Win/Draw/Loss tablebase value
Level: AdvancedThe exact win, draw, or loss outcome that a tablebase assigns to an endgame position.
Distance to mate
Level: AdvancedA metric counting the distance to forced mate when the winner hastens it and the defender delays it.
Depth to Conversion
Level: ExpertA precomputed endgame metric measuring the distance to a capture or promotion, or to mate if it comes first.
Distance to zero
Level: AdvancedA precomputed endgame metric measuring the distance to mate or to the next move that resets the fifty-move counter.
