Screamer Chess

Screamer Chess is a freely distributed PowerPC chess engine by William Bryant, packaged with a Mac front-end, an opening book, elementary endgame tablebases, and complete documentation. By build 57 the engine plays at a tournament-level strength of roughly 2,380 ELO / 2,560 USCF on the author's G3 tower, with a Mac OS X port flagged as in development.

Concept and audience

Screamer is aimed squarely at serious club players who wanted a strong, free, native PowerPC engine on the Mac at a time when most heavyweight chess software was Windows-first. The bundle is essentially a complete chess analysis package: the Screamer engine, an opening book, basic tablebases, and the front-end needed to play, analyse, or annotate games on Classic Mac OS.

Gameplay and features

Build 57's headline addition is a "Log to PGN File" option that streams every game played into a portable game-notation file, making it trivial to feed those games into Exachess or any other chess database. The engine handles standard tournament time controls, take-backs, and analysis mode; the opening book and endgame tablebases extend its play across the game's three phases.

Engine and strength

Build 57 ships a rewritten evaluation function that lifted Screamer's score on standard test suites to 19/25 on CCR, 23/35 on LCT II, 23/30 on BT2630, and 292/300 on WAC at one minute per position -- yielding an average rating around 2,380 ELO / 2,560 USCF on a 266 MHz G3 tower. The engine is PowerPC-only; the read-me notes a Mac OS X compatible version was being prepared at the time of release.

Development and release

Screamer is the personal project of William Bryant (wbryant@ix.netcom.com), distributed through Info-Mac as screamer-chess-57.hqx in game/brd. A companion "Screamer Book" (the opening-book data file) ships separately. The numbered build sequence implies steady iterative releases rather than a marketing-driven version scheme typical of commercial chess software.