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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>The enginecommand function is used for all other communication between
engine and CheckerBoard</title>
</head>
<body>
<h1 style="font-family: "Times New Roman", serif; font-size: 48px; font-style: italic; font-weight: bold; margin-bottom: 20px; margin-top: 15px; color: rgb(0, 128, 192); font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: right; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">CB
API reference</h1>
<h4 style="font-family: Arial, sans-serif; font-size: 14px; font-weight: bold; color: rgb(255, 255, 255); background: rgb(0, 128, 192); padding: 2px; margin-bottom: 0px; margin-top: 4px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Introduction</h4>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">CheckerBoard
is explicitly only designed as an interface to checkers engines, and
CheckerBoard is free. Therefore, CheckerBoard is a good choice for an interface
if you want to develop a checkers engine, because it relieves you from the
hassle of interface programming, and because it gives you the capability to test
your engine against other engines with the engine-engine mode. If you would like
to program an engine for CheckerBoard or if you have already written a checkers
program and want to adapt it to run as engine in CheckerBoard, here is the
documentation of the CheckerBoad API. If you want to use my engine Cake in your
checkers program, you are welcome to do so. There are no restrictions on the use
of cake.dll by third parties - you may also use it in a commercial program. Of
course, cake.dll comes without any warranties, all liabilities are excluded.</p>
<h4 style="font-family: Arial, sans-serif; font-size: 14px; font-weight: bold; color: rgb(255, 255, 255); background: rgb(0, 128, 192); padding: 2px; margin-bottom: 0px; margin-top: 4px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Limitations</h4>
<span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">The
CheckerBoard API is not a well-designed protocol by a professional computer
programmer. I know that it is far from perfect, and if you feel you have a
suggestion for an improvement, feel free to tell me about it. A big hole in the
protocol is that pondering is not supported. Besides that, there is a number of
minor limitations which I do not think are very important. However, if you think
otherwise, please tell me about it.</span>
<h4 style="font-family: Arial, sans-serif; font-size: 14px; font-weight: bold; color: rgb(255, 255, 255); background: rgb(0, 128, 192); padding: 2px; margin-bottom: 0px; margin-top: 4px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The
CheckerBoard API</h4>
<span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">CheckerBoard
expects your engine to be compiled as a dll and to be in the engines
subdirectory under CheckerBoard, and its supporting files should also go there
(helpfiles etc). Your program will see the CheckerBoard directory as the working
directory when it is called from CheckerBoard.</span>
<p><span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">An
engine must support 2 required functions. If your engine plays a different
version than English checkers, you must provide 2 more functions for
multi-version support.<span> </span></span><b style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The
calling convention for all functions is __stdcall.</b></p>
<p>The CheckerBoard install package includes the C++ header file <b>cb_interface.h</b>
that has defnitions for most of the types, function prototypes, and constants
that you need to interface to CheckerBoard. You can #include this file in your
project if your engine is written in C++, or use it as a quick reference even if
you're using a different language.</p>
<h4 style="font-family: Arial, sans-serif; font-size: 14px; font-weight: bold; color: rgb(255, 255, 255); background: rgb(0, 128, 192); padding: 2px; margin-bottom: 0px; margin-top: 4px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Required
Functions</h4>
<span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">The
current CheckerBoard API (version 2) requires the following 2 functions:</span>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><code>int
WINAPI getmove(int board[8][8], int color, double maxtime, char str[1024], int
*playnow, int info, int moreinfo, struct CBmove *move);<br>
int WINAPI enginecommand(char command[256], char reply[1024]);</code><br>
where struct CBmove is defined as follows:</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><code>struct
CBmove<br>
{<br>
int jumps; // number of jumps in this move<br>
int newpiece; // moving piece after jump<br>
int oldpiece; // moving piece before jump<br>
struct coor from,to; // from,to squares of moving piece<br>
struct coor path[12]; // intermediate squares to jump to<br>
struct coor del[12]; // squares where men are removed<br>
int delpiece[12]; // piece type which is removed<br>
};</code></p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><code>struct
coor<br>
{<br>
int x;<br>
int y;<br>
};</code></p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">If
you plan to write an engine that plays English/American checkers, you can
immediately forget about the struct CBmove again.</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The
function getmove gets a move from the engine. <b>getmove</b><span> </span>receives
the current board position in the 2-dimentional array board[8][8], and returns
the position after the engine's response move in the same array. </p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The
side to move is in color.<br>
<br>
Maxtime is the time your program should think<span> </span><b>on average</b><span> </span>for
its move. CheckerBoard does not check the time usage of an engine, which means
you can take as much time as you like on your move if you want - but of course
that's not what the user expects!<br>
<br>
The board position and the side to move use the conventions:</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><code>#define
CB_WHITE 1<br>
#define CB_BLACK 2<br>
#define CB_MAN 4<br>
#define CB_KING 8<br>
#define CB_FREE 0</code></p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">so
for instance if an array entry is 10 that means it is a black king. You can use
statements like<span> </span><code>if board[i][j]==CB_BLACK|CB_KING...</code><span> </span>to
find out if there is a certain piece on a square. The header file cb_interface.h
defines functions coorstonumber() and numbertocoors() so that you can easily
convert between traditional square numbers and CheckerBoard's 2-dimentional
array representation of a board.<br>
<br>
The parameter color is either CB_BLACK or CB_WHITE and tells the engine which
side is to move. <br>
<br>
The next parameter is a pointer to a string. This string is displayed in the
status bar of CheckerBoard. You can use this to display search information. Just
write something like<span> </span><code>sprintf(str,"i am
winning");</code><span> </span>and "i am winning" will be
displayed in the status bar. The status bar is updated every 0.1s in
CheckerBoard. There is no defined format for the string you should display
there, you are completely free. However, I suggest that you do something similar
as Cake does.<br>
The next parameter is a pointer to the integer playnow. You should monitor
playnow and immediately return if it is nonzero. This means that the user has
chosen "Play" in the CheckerBoard menu.<br>
<br>
The next parameter, info, is a bunch of flags which are used for some advanced
stuff:</p>
<ul>
<li>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Bit
0 was originally defined as a "reset moves" message to the engine.
In order to detect draw by repetition, the engine was supposed to keep track
of game moves, and reset its game history when bit 0 was set, because maybe
a new game was started or some other interruption occured to the normal flow
of the game. However this scheme is unsatisfactory because the engine cannot
properly keep track of the game history during other search modes such as
Analysis. In 2021, the "set gamehist" enginecommand was added so
that the engine always has the most current history of reversible moves
before each call to getmove().</li>
<li>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Bit
1 is set if 'exact' has been selected in the 'level' menu. In this case,
your engine should return a move exactly after the time that has been
selected by maxtime, and not take any longer.</li>
<li>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Bits
2 and 3 are used for incremental time control, otherwise known as a Fischer
clock. Additional parameters for incremental time are in the moreinfo
parameter. See cb_interface.h for details on how this works, and a function
to unpack the bits for the initial time and increment values.</li>
</ul>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The
further bits are reserved for future extensions.<br>
<br>
Getmove should return a value between 0 and 3, defined as follows:<br>
<br>
<code>#define CB_DRAW 0<br>
#define CB_WIN 1<br>
#define CB_LOSS 2<br>
#define CB_UNKNOWN 3<br>
<br>
</code>CheckerBoard uses the return value in automated engine matches to
terminate a game when an engine claims a draw, win or loss. When CheckerBoard is
in any other play mode, the return value of getmove is not used.</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">The<span> </span><b>enginecommand</b><span> </span>function
is used for all other communication between engine and CheckerBoard. The
interface uses enginecommand to send a command string to the engine, which
should print a reply into the reply string. Here's a list of the commands your
engine should support:</p>
<ul style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">
<li><b>about</b>: print a short description of your program in the reply
string. This will be displayed in a message box, so you must also provide
the formatting with \n for new lines.</li>
<li><b>get ...</b><span> </span>asks for the value of an option or engine
attribute. See also "set" below. Most settings have both a
"set" and a "get", and they are all documented under
"set". Only the "get" commands that do not have a
corresponding "set" are shown here.
<ul>
<li><b>get protocolversion</b>: print the protocol version number in reply
(currently "2"). This enables the interface to detect older
engines and interact properly with them if the protocol is updated.</li>
<li><b>get gametype</b>: print the game type number of the version of
checkers your engine plays in the reply string. American/English: 21,
Italian: 22, Spanish: 24, Russian: 25, Brazilian: 26.</li>
<li><b>get movelist <fen></b>: returns a list of legal moves in
ASCII format for the the position <fen>. This query is only sent
by CheckerBoard when the gametype is something other than English
checkers. You don't need to handle this for English checkers, but you
should handle it for other variants. The reply should be in the
format: <br>
"movelist <nmoves>,<njumps1>,<oldpiece1>,<newpiece1>,<from sq1>,<to sq1>,<landed sq1>,<cap. sq1>,<cappiece1>,<landed sq2>,<cap. sq2>,<cappiece2>,...;".
Each move terminates in a semicolon. If no moves, the response is "movelist 0".
At startup, CheckerBoard sends a position with no moves and looks for
the exact response of "movelist 0" to confirm that the engine
supports this command. Below are 2 examples from Italian checkers.<br>
Example1: enginecommand "get movelist B:W31:B3"<br>
Response: "movelist 2,0,6,6,3,6;0,6,6,3,7;"<br>
Example2: enginecommand "get movelist B:W11,13,19,21:B6,9"<br>
Response: "movelist 2,2,6,6,9,25,18,13,5,25,21,5;2,6,6,6,22,15,11,5,22,19,5;"</li>
</ul>
</li>
<li><b>help</b>: print the name of a HTML help file in reply. CheckerBoard
will invoke the default HTML viewer to display the file.</li>
<li><b>name</b>: print the name of your engine in the reply string.</li>
<li><b>set option X</b><span> </span>sets an option to X.
<ul>
<li><b>set allscores X</b>: X = 0,1. <span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">Set
to 1 if you want allscores mode (the engine displays a list of all moves
with their scores instead of the normal search info), 0 if you want in
normal mode. The allscores mode is a good tool for a human to help in
analysis.</span></li>
<li><b>set book X</b>: set the book strength. Currently, CheckerBoard
supports values 0...3, meaning no book, all kinds of moves, good moves,
best moves, respectively. How you want to interpret the book strength is
your decision.</li>
<li><b>set bookfile X</b>: set the filename and path of the opening book
file to X. If the opening book file is in the same directory as the
engine DLL, then only the filename is sufficient. Otherwise, the full
path to the file should be included with the filename.</li>
<li><b>set dbmbytes X</b>: set the WLD endgame database cache size to X MiB.</li>
<li><b>set dbpath X</b>: set the path to the WLD files to X. If the path
starts with a drive letter or backslash root specifier then the path is
interpreted as an absolute path, else it is relative to the current
directory.</li>
<li><b>set enable_mtc X</b>: X = 0,1. <br>
Enable or disable the auxiliary endgame database, which might be MTC or
DTW. </li>
<li><b>set enable_wld X</b>: X = 0,1. <br>
Enable or disable the WLD database.</li>
<li><b>set gamehist X</b>: this command is sent by CheckerBoard
immediately before each call to getmove(). The purpose is to inform the
engine of any reversible moves in the recent game history, so that it
can properly detect draws by repetition. It sends the game position after the most recent non-reversible move, followed optionally by any reversible moves that occurred after that position.
Reversible moves are non-capture king moves, so most of the time it just sends the current board position. At the beginning of a game it typically looks like this:<br>
<br>
set gamehist B:W21,22,23,24,25,26,27,28,29,30,31,32:B1,2,3,4,5,6,7,8,9,10,11,12<br>
<br>
Here's an example of what is sent later in the game when there are recent king moves:<br>
<br>
set gamehist B:WK12,K27,30,32:B21,K24,28,K31 24-19 27-24 19-15 12-16<br>
<br>
The position at the end of the FEN setup and optional list of moves
should always be identical to the position that is sent with the
immediately following call to getmove().<br>
</li>
<li><b>set hashsize X</b>: set the hashtable size in MiB.</li>
<li><b>set max_dbpieces X</b>: set the maximum number of pieces of
positions for which the WLD db will be used.</li>
<li><b>set mtcpath X</b>: set the path to the auxiliary endgame db files
to X. If the path starts with a drive letter or backslash root specifier
then the path is interpreted as an absolute path, else it is relative to
the current directory.</li>
<li><b>set searchthreads X</b>: set the number of search threads that the
engine should use.</li>
<li><b>set solve X</b>: X = 0,1. <br>
Enable or disable solve mode. In this mode, the engine search is
optimized for "problem" positions where there might be several
sacrifices before the path to the solution is clear. In a normal search,
these positions are sometimes difficult to solve because the search
depth is reduced along paths that look inferior due to a substantial
loss of material.</li>
</ul>
</li>
</ul>
<span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">Your
engine may choose not to implement some of the enginecommand commands of the
protocol. If your engine does not handle an enginecommand argument sent to it by
CheckerBoard, the function should return the value 0. As a general rule, you
should print some acknowledgment in reply that you did handle a command. This is
useful if you ever want to use the engine command dialog, which displays the
reply of the engine. If it handles the command, it should return 1 to let
CheckerBoard know that it understood and processed the command.<br>
</span>
<h4><span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline; float: none">Time
Control</span></h4>
<p>In normal searches, CheckerBoard sends the selected move time parameter with
getmove(), and the engine should try to use approximately that time for its
search, but CheckerBoard doesn't check it and it doesn't care if the time used
is much different than the value sent. During engine matches with a fixed time
per move setting, CheckerBoard handles the search times a little differently. It
keeps track of a clock for each opponent. It increases each engine's clock time
by the per move time setting before each move, and it subtracts the measured
search time from the engine's clock after getmove() returns. CheckerBoard sends
a search time value to getmove that is based on the remaining clock time and the
per move increment as described in the table below.</p>
<table border="1" width="49%">
<tr>
<td width="48%" bgcolor="#FFCC99" align="center">Clock time</td>
<td width="52%" bgcolor="#FFCC99" align="center">value sent to getmove()</td>
</tr>
<tr>
<td width="48%" align="center">less than 40% of increment</td>
<td width="52%" align="center">40% of increment</td>
</tr>
<tr>
<td width="48%" align="center">between 40% and 100% of increment</td>
<td width="52%" align="center">clock</td>
</tr>
<tr>
<td width="48%" align="center">greater than increment</td>
<td width="52%" align="center">increment + (clock - increment) / 2.5</td>
</tr>
</table>
<p> </p>
<h4 style="font-family: Arial, sans-serif; font-size: 14px; font-weight: bold; color: rgb(255, 255, 255); background: rgb(0, 128, 192); padding: 2px; margin-bottom: 0px; margin-top: 4px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Multi-Version
Support Functions</h4>
<span style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">If
you want to write an engine that plays a different version of checkers than
English, you must add another function to your dll:</span><code style="color: rgb(0, 0, 0); font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><br>
int WINAPI islegal(int board[8][8], int color, int from, int to, struct CBmove
*move);</code>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">In
addition to this, your engine command function must recognize the command<span> </span><b>get
gametype</b><span> </span>and return the appropriate number for your
version of checkers.<br>
<b>Islegal</b><span> </span>tells CheckerBoard about the rules of your
version of checkers. When the user wants to play a move from 'from' to 'to',
islegal is called. You must use your move generator to find out if 'color' can
play this move on 'board'. If yes, return 1, else 0. If the move is legal, you
must also tell CheckerBoard what it is, so that it can animate the move
properly. You do this by filling in the CBmove struct.</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Note
that the use of the islegal() function does not properly handle positions where
there is more than one way that a capture move can be made between the same
'from' and 'to' squares. For this reason, in 2018 the "get movelist"
engincommand was added to CheckerBoard. Engines for Non-English variants should
implement this command. See the description of <b>enginecommand</b> above.</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">In
case that this is not clear enough, study the code of simple checkers, which is
included in the CheckerBoard installation. Simple Checkers is an example for an
English engine. If you plan to play a different version, look at the source code
for dama to see how this works.</p>
<p style="color: rgb(0, 0, 0); font-family: Verdana, Georgia, sans-serif; font-size: 14px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">Once
you have finished your engine, you must copy the dll into the CheckerBoard
folder and select your engine with 'engine->select...'. Of course I would
love to hear from you if you do write an engine for CheckerBoard. If you do,
please send me a mail to<span> </span><i>nospam1 at fierz dot ch</i>. I
would like to link to your page, or, if you don't have one, I would put your
engine on my server.</p>
<p> </p>
<p> </p>
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