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1 Pachi can refer to: a simple modular framework for programs playing
2 the game of Go/Weiqi/Baduk, and a reasonably strong engine built
3 within this framework.
6 Installation
7 ------------
9 To build Pachi, simply type:
11 make
13 The resulting binary program `pachi` is a GTP client; connect to it
14 with your favorite Go program interface (e.g. gogui or qgo), or use
15 kgsGtp to connect it to KGS. (DO NOT make the GTP interface accessible
16 directly to untrusted users since the parser is not secure - see the
17 HACKING file for details.)
19 The pachi program can take many parameters, as well as the particular
20 engine being used; the defaults should be fine for initial usage,
21 see below for some more tips.
23 In case you hit compilation issues (e.g. when building on MacOS/X)
24 or want to change the build configuration, check the user configurable
25 section at the top of the Makefile.
28 Engine
29 ------
31 The default engine plays by Chinese rules and should be about
32 3d KGS strength on 9x9. On 19x19, it might be about KGS 2k, assuming
33 reasonable hardware, e.g. two-core Athlon64 machine. On a higher-end
34 (e.g. six-way Intel i7) machine, it can hold a solid KGS 1d rank.
35 When using a large cluster (64 machines, 20 cores each), it maintains
36 KGS 3d and has won a 7-stone handicap game against Zhou Junxun 9p.
38 By default, Pachi currently uses the UCT engine that combines
39 Monte Carlo approach with tree search; UCB1AMAF tree policy using
40 the RAVE method is used for tree search, while the Moggy playout
41 policy using 3x3 patterns and various tactical checks is used for
42 the semi-random Monte Carlo playouts.
44 At the same time, we keep trying a wide variety of other approaches
45 and enhancements. Pachi is an active research platform and quite a few
46 improvements have been already achieved. We rigorously play-test new
47 features and enable them by default only when they give a universal
48 strength boost.
51 By default, Pachi will run on a single CPU core, taking up to 1.4GiB
52 of memory, not pondering and taking completely arbitrary amount of time
53 per turn. You can adjust these parameters by passing it extra command
54 line options:
56 ./pachi -t _1200 threads=8,max_tree_size=3072,pondering
58 This will make Pachi play with time settings 20:00 S.D. (unless it
59 gets told otherwise over GTP), with 8 threads, taking up to 3GiB
60 of memory (+ several tens MiB as a constant overhead) and thinking
61 during the opponent's turn as well.
63 Pachi can use an opening book in a Fuego-compatible format - you can
64 obtain one at http://gnugo.baduk.org/fuegoob.htm and use it in Pachi
65 with the -f parameter:
67 ./pachi -f book.dat ...
69 You may wish to append some custom Pachi opening book lines to book.dat;
70 take them from the book.dat.extra file. If using the default Fuego book,
71 you may want to remove the lines listed in book.dat.bad.
73 For now, there is no comprehensive documentation of options, but you
74 can get a pretty good idea by looking at the uct_state_init() function
75 in uct/uct.c - you will find the list of UCT engine options there, each
76 with a description. At any rate, usually the three options above are
77 the only ones you really want to tweak.
80 Except UCT, Pachi supports a simple idiotbot-like engine and an example
81 treeless MonteCarlo-player. The MonteCarlo simulation ("playout")
82 policies are also pluggable, by default we use the one that makes use of
83 heavy domain knowledge.
85 Other special engines are also provided:
86 * a "distributed" engine for cluster play; the description at the top of
87 distributed/distributed.c should provide all the guidance
88 * a simple "replay" engine that will simply play moves according
89 to the playout policy suggestions
90 * a simple "patternplay" engine that will play moves according to the
91 learned patterns
92 * few other purely for development usage
95 Pachi can be used as a test opponent for development of other go-playing
96 programs. For example, to get the "plainest UCT" player, use:
98 ./pachi -t =5000 policy=ucb1,playout=light,prior=eqex=0,dynkomi=none
100 This will fix the number of playouts per move to 5000, switch the node
101 selection policy from ucb1amaf to ucb1 (i.e. disable RAVE), switch the
102 playouts from heuristic-heavy moggy to uniformly random light, stop
103 prioring the node values heuristically, and turn off dynamic komi.
105 You can of course selectively re-enable various features or tweak this
106 further. But please note that using Pachi in this mode is not tested
107 extensively, so check its performance in whatever version you test
108 before you use it as a reference.
110 Note that even in this "basic UCT" mode, Pachi optimizes tree search
111 by considering board symmetries at the beginning. Currently, there's no
112 easy option to turn that off. The easiest way is to tweak board.c so
113 that board_symmetry_update() has goto break_symmetry at the beginning
114 and board_clear has board->symmetry.type = SYM_NONE.
117 Analysis
118 --------
120 Pachi can also help you analyze your games by being able to provide
121 its opinion on various positions. The user interface is very rudimentary,
122 but the ability is certainly there.
124 There are currently several Pachi interfaces provided for this purpose.
126 Winrate Development
127 ~~~~~~~~~~~~~~~~~~~
129 Pachi can evaluate all moves within a given game and show how
130 the winrates for both players evolved - i.e. who was winning at which
131 game stage. This is implemented using the `tools/sgf-analyse.pl` script.
132 See the comment on top of the script about its usage.
134 Move Ranking
135 ~~~~~~~~~~~~
137 Pachi can evaluate all available moves in a given situation
138 and for each give a value between 0 and 1 representing perceived
139 likelihood of winning the game if one would play that move. I.e. it can
140 suggest which moves would be good and bad in a single given situation.
142 To achieve the latter, note the number of move at the situation you
143 want to evaluate and run the `tools/sgf-ratemove.sh` script.
144 See the comment on top of the script about its usage.
146 Pattern Move Hinting
147 ~~~~~~~~~~~~~~~~~~~~
149 Pachi can show instantenous pattern-based move suggestions very much
150 like for example Moyo Go Studio (though of course without a GUI).
151 You can use the Move Ranking method above (tools/sgf-ratemove.sh),
152 but pass it an extra parameter '-e patternplay'.
155 Framework
156 ---------
158 The aim of the software framework is to make it easy to plug your
159 engine to the common infrastructure and implement your ideas while
160 minimalizing the overhead of implementing the GTP, speed-optimized
161 board implementation, etc. Also, there are premade random playout
162 and UCT tree engines, so that you can directly tweak only particular
163 policies. The infrastructure is pretty fast and it should be quite
164 easy for you (or us) to extend it to provide more facilities for
165 your engine.
167 See the HACKING file for a more detailed developer's view of Pachi.
169 Also, if you are interested about Pachi's architecture, algorithms
170 etc., consider taking a look at Petr Baudis' Master's Thesis:
172 http://pasky.or.cz/go/prace.pdf
175 Licence
176 -------
178 Pachi is distributed under the GPLv2 licence (see the COPYING file for
179 details and full text of the licence); you are welcome to tweak it as
180 you wish (contributing back upstream is welcome) and distribute
181 it freely, but only together with the source code. You are welcome
182 to make private modifications to the code (e.g. try new algorithms and
183 approaches), use them internally or even to have your bot play on the
184 internet and enter competitions, but as soon as you want to release it
185 to the public, you need to release the source code as well.
187 One exception is the Autotest framework, which is licenced under the
188 terms of the MIT licence (close to public domain) - you are free to
189 use it any way you wish.