michaelb7/crafty

Purpose and entry points

Crafty is a native ANSI C chess engine descended from Cray Blitz, built around bitboard position representation and performance-oriented search. The executable lifecycle begins in src/main.c, initializes engine-wide state in src/init.c, and runs command/game control through src/crafty.c and src/input.c.

Core engine state and position transitions

Shared chess types, board state, and engine declarations are centralized in src/chess.h, src/data.h, and src/data.c. Position setup and legality boundaries are handled by src/setboard.c and src/validate.c. Search mutates positions through reversible move application in src/make.c and src/unmake.c; this is the critical state-integrity boundary.

Move generation and tactical primitives

Legal candidate generation is provided by src/movgen.c, backed by attack/bitboard computations in src/attacks.c and static-exchange evaluation in src/see.c. These components feed both full search and tactical extensions, while src/next.c controls move ordering/selection during node expansion.

Search pipeline

Root-level search orchestration is in src/root.c and iterative deepening in src/iterate.c. The main recursive alpha-beta-style search resides in src/search.c, with tactical leaf search in src/quiesce.c and pruning/reduction policy in src/reduce.c. Time and stop control form a cross-cutting control boundary through src/time.c and src/interrupt.c.

Evaluation, learning, and search memory

Static position scoring is implemented in src/evaluate.c with its interface in src/evaluate.h. Transposition caching is owned by src/hash.c; historical ordering and adaptive information are maintained in src/history.c and src/learn.c. Search probes can therefore use hash/history data before expanding moves, while evaluation supplies scores at leaves and selected search nodes.

External chess knowledge and execution environment

Opening-book support is in src/book.c, consuming repository opening data such as openings/new2500.epd and openings/4000_openings_legacy.epd. Endgame tablebase integration is represented by src/tbprobe.c, src/tbcore.c, and src/tbchess.c (Syzygy-derived code). EPD parsing/testing boundaries are in src/epd.c and src/epdglue.c.

Runtime, concurrency, and builds

The engine is a command-line native program using ANSI C plus limited Unix I/O; platform/build variants are provided by src/Makefile, src/Makefile-official, and src/makefile.win. Parallel search infrastructure is isolated in src/thread.c, while user-visible command output and analysis interaction are handled by src/output.c and src/analyze.c.