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Phalanx is a chess playing program
Copyright (c) 1997, 1998 Dusan Dobes
LICENSE AND WARRANTY
- Phalanx is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
- Phalanx is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
along with Phalanx; see the file COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA.
COMPILING
is simple, at least under Linux. Just type `make'. If you have problems
on a platform other than Linux, i will not be able to help you.
INTERFACE, COMMAND LINE OPTIONS
Phalanx is xboard compatible. Running with xboard: 'xboard -fcp phalanx'.
Note that permanent brain (pondering) is off by default. If you want
Phalanx to think on opponent's time, type 'phalanx -p+'. It's better to stop
permanent brain in both programs, when playing Phalanx against another
program on a machine with one CPU.
It's also possible to run phalanx without xboard. Do "phalanx -h" to get
a list of command line options. One important command of phalanx's ASCII
interface is "help".
MORE ABOUT INTERFACE
I'm trying to write an interface that fits following three requirements:
- xboard compatibility
- shell-like interface that allows running commands in a batch. It's very
useful for testing. Example: look into the file test.fin. It's a set
of chess problems and solutions. You can simply send this file to
Phalanx's stdin:
$ phalanx -c+ -o- -b- -f10 < test.fin | tee result
( Where: -c+ .... use cpu time
-o- .... don't use polling input
-b- .... no opening book
-f10 ... fixed time 10 seconds per move )
Watch how it works.
- Acceptable ASCII interface.
OPENING BOOK
From version VI, there are two book files - primary (pbook.phalanx), and
secondary (sbook.phalanx). You can specify book directories via command line
(-P, -S) or use environment variables PHALANXPBOOKDIR and PHALANXSBOOKDIR.
Otherwise Phalanx tries to find its book files in current directory
(./book.phalanx, ./sbook.phalanx) and finally in compiled-in directory
(/usr/local/lib/phalanx). You can change the compiled-in directory in
makefile.
- pbook.phalanx is 'hand'-written, text book. One line per position, sorted.
This time, it's bigger than really needed, because it was the only book
file till version V. The size will be smaller and the line format will
change to EPD+SAN in future.
- sbook.phalanx is binary book, generated from large PGN files. Six bytes
per move (4 hash key, 2 move). You can generate your own sbook.phalanx
with bcreate, like this:
$ ./bcreate < manyGMgames.pgn
or:
$ ./bcreate 1250000 < manyGMgames.pgn
( where 1250000 is internal buffer size in cells. One cell takes 8 bytes.
Bigger is better, only if it's too big a part of the buffer is unused.
E.g. 1250000 is enough to parse Crafty's 'medium' book source - 29MB. )
A position is first searched in pbook.phalanx. Only if it's not found there,
sbook.phalanx is searched.
PORTABILITY
Phalanx is developed under GNU C & GNU Make. It's probably possible to
compile it on many different platforms, but today i have no oportunity
to try it on any other platform than Linux. If you have ideas how to
make it's portability better, let me know.
INSIDE THE MACHINE
Phalanx uses (traditional) 10x12 board implementation. There are three
often used board implementations: "8x8" (GNU Chess), "bitboard" (Crafty),
and "10x12" (Nimzo, Phalanx). In short, "10x12" is easy to implement and
the code is small (==fast on PC). The engine uses many well known
techniques: PVS (principal variation search), transposition/killer table,
static-eval cache, history killers, SEE (static exchange evaluator), null
move pruning, forward pruning, chess-specific extensions.
AUTHOR
Dusan Dobes, dobes@math.muni.cz
HISTORY
The rest of this file is history of Phalanx.
I First version to play a legitimate game, it finally knows all rules.
19970304 I spent a lot of time on tuning transposition table code and
extensions. The program scores 78% at large Reinfeld's test set, 10 s
per move, on 486+/150.
II Two killer heuristics added: well known history killers (modified)
199704?? and `reaction' killers (the killer is connected to the previous enemy
move). The tree search is faster, especially at `quiet' positions.
Hashtable presearch. Modified hashentry replacement strategy. Better
evaluation function, it now knows more about passed pawns, the
endgame play is much stronger. Fixed bug at 7-th row pawn push
extension routine. Faster output - using sprintf() to prepare the
output and then only one printf. New command line options: -t, -T to
set the hashtable size.
III Permanent brain (pondering). King safety evaluation. Hung pieces
19970529 static evaluation. Null move pruning. Forward pruning. Better time
heuristics - forced moves are played quickly. New cmd-line options:
-f, -x, -p, -s.
IV New option -c to determine whether to use cpu or real time. The
19970721 internal timing resolution changed to 1/100 of a second. Xboard
compatible editing position. Removed en-passant capture from
quiescence search. Changes in static-eval function. Piece list
implemented - speedup is between 0 and 20%; more in endgame. Pinned
pieces static evaluation. Better evaluation of weak pawns. Trapped
bishop and knight evaluation. Bugfix at extending check evasions.
Bugfix: development bonus was computed but not added to total
evaluation. Output change: '!' means turn, '!!' means value out of
window.
V Mostly interface changes, no big improvement in playing strength.
19970803 Xboard compatibility fixes: 'post' is no more switch, new command
'remove'. Fixed command 'level': 'level 0 5 0' (five minutes per
game) should work, also increment (ICS) levels ('level 0 2 12').
Increment can be given at command line. New option -o (polling
input) - when running tests, phalanx needs -o-. New feature of
autotesting: all incorrect results are written into file
'notfound.fin'. Small output changes for better compatibility with
xboard 3.6.2. Eliminated some bad turns in evaluation. Better king
safety evaluation - counting safe checks available.
VI Fixed small efficiency bug in evaluate.c. Improved time heuristics
19970915 for increment (ICS) levels. Optimized hashing - about 5% overall
speedup. Fixed bug in ptime(). User is now allowed to continue play
even if the position is drawn by 3-rep., material, or 50 moves rule.
Fixed bug - Draw requests are now always ignored, not always accepted
:-). Xboard-compatible 'Illegal move' message. Binary opening book,
created from PGN by bcreate. This distribution is bigger than any
previous because it contains a small example of binary book
('sbook.phalanx', 174kB, 29634 moves). SAN input accepted. Static
evaluation now better understands middlegame positions without
castling. Added pre-computed tables into static evaluation -> about
5% speed improvement. 'Show thinking' mode now shows also a list of
book moves if there's a book entry. I have played a match with
previous version (64 games, 2 minutes, increment 12 seconds, on
a 486+/150, via xboard, no pondering), new version wins 38.5-25.5.
VII Courtesy of Pavel Janik ml., new command 'fen'. Bugfix in command
19971022 line parser, 'phalanx 0 2 12' now works. Better time controls: added
hard time limit to avoid being flagged. Pondering bugfix: Phalanx
was pondering O-O, but opponent played O-O-O; the move check was
incorrect and Phalanx thought that O-O was played; this resulted in
'Illegal move' message few moves later. More pondering safety: the
move to be pondered is now checked for legality, before this fix it
was simply taken from PV (if present), but PV is not always 100%
correct. More PV safety: search cannot be interrupted during the
first iteration, the abort is delayed until the first iteration is
finished. New options: -r <resign value>, -b <+/-> to set opening
book on/off. New commands hard/easy to set pondering on/off.
Optimized do_move(): 3% speedup in test positions. Search
optimization: null move is not played if the value in hash table
entry is too low. Output bugfix: output is now readable even at long
time searches. SEE (Static Exchange Evaluator) and more pruning in
quiescence search. RoboFICS compatible commands 'white' and 'black'.
Routine for evaluating pawn endgames. New extension trick that helps
in some horizon-effect type positions, it's based on measuring
difference between current score and null move result; if current
score is much better, the side to move must be under threat and the
line is extended, similar trick is also in gnuchess.
VIII Fixed bug in search(): eliminated useless re-searches -> about 3%
19971103 speed improvement. Noise level is now in centiseconds, not in nodes.
Improved horizon-effect extensions. endgame.c: new endgame
knowledge, mostly for endgames with minor pieces and pawns: knight
and bishop mating, knight+knight (draw), minor vs. minor (draw),
minor vs. pawn (draw, but still needs some work, sometimes a pawn
wins against a knight), onepawn() as a special case of pawns(), bad
bishop (bishop + rook pawn), basics for R+P vs. R, bishops with
opposite colors (this is often drawish ending). New penalty for
moving castling-side pawns in middlegame.
IX Function smove() is now used in both binary book and hashing code, it
19971205 is cleaner and easier to read, the binary is smaller with this.
Bugfix: Phalanx now does not ponder move that leads into a terminal
position (checkmate, stalemate), this fixes some unexpected quits
(I hope all of them). Added more limits to horizon-effect extension
trigger - there was so many extensions, that version VIII was
actually weaker than previous versions, because of lower nominal
search depth; these extensions are now used only for major threats.
Static eval cache entry is now packed into 4 bytes instead of 8 ->
the cache eats only 256K (512K before this).
X Bugfix in static evaluation of trapped knight at [AH]7. Better
19980108 evaluation of trapped bishop ([AH]7) and knight ([AH][87]), now it's
using the static exchange evaluator. Time allocation: alloc more
time (+1/8) if pondering is on. Better understanding of 'trade-down'
bonus - if there are no pawns, you often need a rook more to win the
game, a minor piece is not enough. Shallower extensions resulting in
greater average search depth. Easy levels: use new command line
option -e <1...100> to select an easy level; 1 is the strongest and
100 is the easiest one, Phalanx tries to make human-like blunders.
Minor changes in resigning. Clean up in pbook.phalanx, deleted over
100 positions. Killer heuristics now uses the SEE. Bugfix in
endgame.c: trade bonus did not work for kings and pawns endgames.
Simple learning, can be activated by -l+ option; it is off by
default, because it's very experimental version. New version wins
engine-engine match with version IX 23:17 (tc 2, inc 8, 486+/150,
no learning, no pondering).
XI Courtesy of Milan Zamazal: long options and user-friendly handling of
19980125 book files - you can now use environment variables or command line
options. Bugfix in trade bonus: endgame KQ-KBPP was evaluated only
about +1.10, but the stronger side is winnig here even without pawns,
now it's >+3.00 and Phalanx can solve this Dufrense&Mieses study:
8/3Np3/7P/1p3P2/1k6/5K2/1b6/8/w Pf5f6. Deeper overall extensions,
+10% of ply. More check evasion extensions. Wider window for 'lazy
evaluation', search is now slower but stable. Minor fixes in forward
and null move pruning. Zero-width search modified for root moves,
actually it's no more zero-width; this eliminates some 'blind turns'
(a move is evaluated as >=(Alpha+1), but the engine cannot prove it
in re-search in full [Alpha,Beta] window). Minor changes in static
evaluation. Bugfix in time allocation of increment levels. Changed
time heuristics to use more time.
XII More pruning in quiescence search: moves that have little chance to
19980301 return the value over alpha are not generated. Permanent brain is
now really 'permanent', if there is no move to ponder in the PV,
Phalanx uses short search to pick a move and ponders it. Bugfix:
occasional zero division at very fast time controls, like 10s/game.
Some puts() replaced with printf(), puts() is buggy in my gcc (2.7.2)
and causes sigsegv when interrupted and called again during the
interrupt. Optimized null move, this speeds up the engine. Easy
levels now use nodes instead of centiseconds for measuring time, the
playing strength of easy levels does not depend on cpu power and
cpu load. Resigning now works with RoboFics (via 'tellics resign').
Updated FSF address in docs.
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