Chronology

versionreleasedtechnical notesrating*
0.6.02021.11.25Massive line by line code cleaning and optimization; no more crashes or stalls. Time control highly improved, no more time losses. Move generator improved with magic bitboards for sliders; perft is now very fast. Search improved, better history management, thinking output highly improved. Better evaluation. Console mode: adjusted codepage to work in more systems; better graphics, big board and figurines always enabled; new commands (bench, eval, kiwi, unmake) and integration with UCI commands; perft suite and test suite now run in an automated way. UCI mode: added go nodes, removed ponder management, go infinite may be invoked with just go. WinBoard mode: added memory, undo and ? (move now) commands.2500 (est.)
0.5.92021.08.05First 64 bit version. Search slightly tuned and historic crash bug fixed. Material and mobility evaluation revised. The book has been temporarily removed.2324
0.5.8c2014.06.30Bugs in evaluation and in quiescence search found and fixed. Hash size is now adjustable from 16 to 512 MB, default 256. Statistical piece/square move table removed. Wrong "mate in" value was displayed in XBoard mode. Tuned most parameters. Stop (move now) command has been implemented.2185
0.5.8c2014.06.12Bugs fixed in version 0.5.8.c released on 2014.06.30: some overflows cause crashes.
0.5.8b2014.06.06Bug fixed in version 0.5.8c: EP flag wrongly updated in making/unmaking null moves, causing bad play in ignoring opponents' EP recaptures.
0.5.8a2014.06.02Bug fixed in version 0.5.8b: UCI mode isn't working in some GUI's.
0.5.82014.06.01Bugs fixed in version 0.5.8a: book is disabled and hash used is wrongly displayed.
0.5.72010.01.18Added UCI mode. Hash size is now adjustable from 1 to 256 MB, default 128. Emergency book removed. For debugging and tuning purposes, evaluation suite command added. Move order improved, also using a statistical piece/square move table.1964
0.5.6a2007.02.20Hash 64 MB fixed. Eval fixed. This version works only when the book is available.1933
0.5.5cct2007.02.17New deep eval. New book format, 4 times more compact. This version works only when the book is available.1766
0.5.52007.02.13Small improvements and optimizations.1824
0.5.4a2007.02.05Many code optimizations. Time management: now the engine tries to optimize the allotted time for the whole game. Quiescence search now ignores losing captures, thanks to a fast SEE implementation. Move generator has been highly optimized, with distinct check evasions, captures/queen promotions and normal moves generation; fast Perft and Divide commands added. Piece-square evaluation improved. Aspiration search, zero window and basic search extensions and reductions. A compact opening book is now included (2.6 MB zipped); embedded emergency opening book, automatically selected if no book is found. Syntax and legality check for Setboard command. SAN moves representation with better PV display. SAN input accepted and checked. Detailed search statistics. Console mode with color display and many debugging commands. Testsuite command with detailed results. Engine logo has been slightly changed.1722
0.5.42007.02.03Bugs fixed in version 0.5.4a: on some GUIs, the engine fails to play as Black; WinBoard I/O management should be completely rewritten. WinBoard crushes if the book isn't found. PV move numbers displayed are wrong. A forced move isn't played immediately. Castling is displayed with the wrong symbol (0-0 instead of O-O), with Arena GUI not recognizing the move; reported by Tony Mokonen, Carlos Pagador and Hans Eriksson. Black's kingside castling wrongly alters the vertical rotated bitboard, causing mistakes in generation of moves where a1 is the destination square; discovered by myself after thousands of tests.
0.5.32006.06.147-ply alpha-beta search and null moves (R=3).1242
0.5.22006.06.13Added 5-ply alpha-beta full search.1221
0.5.1b2006.06.11Added a 2-ply full search to test piece-square table and makemove/unmakemove routines.1035
0.5.12006.06.11Bug fixed in version 0.5.1b: unmakemove in one game out of 200 crashes.
0.5.02006.06.10The engine has been completely rewritten, in Delphi and ASM, and now is based on rotated bitboards. This first release just plays a random move (captures and castling first) to test movegen, makemove and WinBoard communication routines.N/A
0.4.42004.07.233-ply alphabeta search plus 3-ply quiescent search.1228
0.4.32004.07.19Replaced 3-ply minimax search with 4-ply alphabeta search.N/A
0.4.22004.07.13Added piece-square evaluation.1169
0.4.12004.07.11Added 3-ply minimax search, with material only evaluation.1073
0.3.22004.07.05Added an opening book, with about 3 millions positions. Size: 23 MB, disk space needed: 130 MB. Without the book, this version is identical to 0.2.2. The book is no longer available.826
0.3.12004.07.05Bugs fixed in version 0.3.2: always the best move is played from the book; thinking isn't displayed in WinBoard.
0.2.22004.07.03Sorts the legal moves and plays a gaussian-random one. Released to test the move ordering.839
0.2.12004.07.02Bugs fixed in version 0.2.2: taking a Rook on its original square doesn't clear the castle-allowed flag; the WinBoard command "computer" isn't recognized.
0.1.12004.06.30Plays a random move. Released to test the move generator. Engine written in Free Pascal.710
* CCRL Blitz rating for Protej 0.5.7 and higher; private 1'+1" tournaments Elo estimates up to Protej 0.5.6a