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Writing a chess program in 99 steps
step 58: command.cpp
#ifndef _CRT_SECURE_NO_DEPRECATE
#define _CRT_SECURE_NO_DEPRECATE 1
#endif
#include <iostream>
#include "defines.h"
#include "protos.h"
#include "extglobals.h"
#include "board.h"
#include "timer.h"
void readCommands()
{
int nextc;
if (board.nextMove == WHITE_MOVE)
{
std::cout << "wt> ";
}
else
{
std::cout << "bl> ";
}
std::cout.flush();
// ===========================================================================
// Read a command and call doCommand:
// ===========================================================================
while ((nextc = getc(stdin)) != EOF)
{
if (nextc == '\n')
{
CMD_BUFF[CMD_BUFF_COUNT] = '\0';
while (CMD_BUFF_COUNT)
{
if (!doCommand(CMD_BUFF)) return;
}
if (board.nextMove == WHITE_MOVE)
{
std::cout << "wt> ";
}
else
{
std::cout << "bl> ";
}
std::cout.flush();
}
else
{
if (CMD_BUFF_COUNT >= MAX_CMD_BUFF-1)
{
std::cout << "Warning: command buffer full !! " << std::endl;
CMD_BUFF_COUNT = 0;
}
CMD_BUFF[CMD_BUFF_COUNT++] = nextc;
}
}
}
BOOLTYPE doCommand(const char *buf)
{
Move move;
Timer timer;
U64 msStart;
U64 msStop;
U64 perftcount;
char userinput[80];
int i, number;
// =================================================================
// return when command buffer is empty
// =================================================================
if (!strcmp(buf, ""))
{
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// help, h, or ?: show this help
// =================================================================
if ((!strcmp(buf, "help")) || (!strcmp(buf, "h")) || (!strcmp(buf, "?")))
{
std::cout << std::endl << "help:" << std::endl;
std::cout << "black : BLACK to move" << std::endl;
std::cout << "cc : play computer-to-computer " << std::endl;
std::cout << "d : display board " << std::endl;
std::cout << "exit : exit program " << std::endl;
std::cout << "eval : show static evaluation of this position" << std::endl;
std::cout << "game : show game moves " << std::endl;
std::cout << "go : computer next move " << std::endl;
std::cout << "help, h, or ? : show this help " << std::endl;
std::cout << "info : display variables (for testing purposes)" << std::endl;
std::cout << "move e2e4, or h7h8q : enter a move (use this format)" << std::endl;
std::cout << "moves : show all legal moves" << std::endl;
std::cout << "new : start new game" << std::endl;
std::cout << "perf : benchmark a number of key functions" << std::endl;
std::cout << "perft n : calculate raw number of nodes from here, depth n " << std::endl;
std::cout << "quit : exit program " << std::endl;
std::cout << "r : rotate board " << std::endl;
std::cout << "readfen filename n : reads #-th FEN position from filename" << std::endl;
std::cout << "sd n : set the search depth to n" << std::endl;
std::cout << "setup : setup board... " << std::endl;
std::cout << "undo : take back last move" << std::endl;
std::cout << "white : WHITE to move" << std::endl;
std::cout << std::endl;
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// black: black to move
// =================================================================
if (!strcmp(buf, "black"))
{
board.nextMove = BLACK_MOVE;
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// d: display board
// =================================================================
if (!strcmp(buf, "d"))
{
board.display();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// eval (do a static evaluation of the board)
// =================================================================
if (!strcmp(buf, "eval"))
{
number = board.eval();
std::cout << "eval score = " << number << std::endl;
#ifdef WINGLET_DEBUG_EVAL
board.mirror();
board.display();
i = board.eval();
std::cout << "eval score = " << i << std::endl;
board.mirror();
if (number != i) std::cout << "evaluation is not symmetrical! " << number << std::endl;
else std::cout << "evaluation is symmetrical" << std::endl;
#endif
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// exit or quit: exit program
// =================================================================
if ((!strcmp(buf, "exit")) || (!strcmp(buf, "quit")))
{
CMD_BUFF_COUNT = '\0';
return false;
}
// =================================================================
// go: computer next move
// =================================================================
if (!strcmp(buf, "go"))
{
move = board.think();
if (move.moveInt)
{
makeMove(move);
board.endOfGame++;
board.endOfSearch = board.endOfGame;
}
board.display();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// game: show game moves
// =================================================================
if (!strcmp(buf, "game"))
{
if (board.endOfGame)
{
for (i = 0 ; i < board.endOfGame ; i++)
{
std::cout << i+1 << ". ";
displayMove(board.gameLine[i].move);
std::cout <<std::endl;
}
}
else
{
std::cout << "there are no game moves" << std::endl;
}
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// moves: show all legal moves
// =================================================================
if (!strcmp(buf, "moves"))
{
board.moveBufLen[0] = 0;
board.moveBufLen[1] = movegen(board.moveBufLen[0]);
std::cout << std::endl << "moves from this position:" << std::endl;
for (i = board.moveBufLen[0]; i < board.moveBufLen[1]; i++)
{
makeMove(board.moveBuffer[i]);
if (isOtherKingAttacked())
{
unmakeMove(board.moveBuffer[i]);
}
else
{
std::cout << i+1 << ". " ;
displayMove(board.moveBuffer[i]);
std::cout << std::endl;
unmakeMove(board.moveBuffer[i]);
}
}
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// move (do a move) [console mode only]
// =================================================================
if (!strncmp(buf, "move", 4))
{
sscanf(buf+4,"%s",userinput);
// generate the pseudo-legal move list
board.moveBufLen[0] = 0;
board.moveBufLen[1] = movegen(board.moveBufLen[0]);
if (isValidTextMove(userinput, move)) // check to see if the user move is also found in the pseudo-legal move list
{
makeMove(move);
if (isOtherKingAttacked()) // post-move check to see if we are leaving our king in check
{
unmakeMove(move);
std::cout << " invalid move, leaving king in check: " << userinput << std::endl;
}
else
{
board.endOfGame++;
board.endOfSearch = board.endOfGame;
board.display();
}
}
else
{
std::cout << " move is invalid or not recognized: " << userinput << std::endl;
}
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// info: display variables (for testing purposes)
// =================================================================
if (!strcmp(buf, "info"))
{
info();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// moves: show all legal moves
// =================================================================
if (!strcmp(buf, "moves"))
{
board.moveBufLen[0] = 0;
board.moveBufLen[1] = movegen(board.moveBufLen[0]);
std::cout << std::endl << "pseudo-legal moves from this position:" << std::endl;
for (i = board.moveBufLen[0]; i < board.moveBufLen[1]; i++)
{
std::cout << i+1 << ". " ;
displayMove(board.moveBuffer[i]);
std::cout << std::endl;
}
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// new: start new game
// =================================================================
if (!strcmp(buf, "new"))
{
dataInit();
board.init();
board.display();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// perft n : calculate raw number of nodes from here, depth n
// =================================================================
if (!strncmp(buf, "perft", 5))
{
sscanf(buf+5,"%d", &number);
std::cout << " starting perft " << number << "..." << std::endl;
timer.init();
board.moveBufLen[0] = 0;
#ifdef WINGLET_DEBUG_PERFT
ICAPT = 0;
IEP = 0;
IPROM = 0;
ICASTLOO = 0;
ICASTLOOO = 0;
ICHECK = 0;
#endif
msStart = timer.getms();
perftcount = perft(0, number);
msStop = timer.getms();
std::cout << "nodes = " << perftcount << ", " << msStop - msStart << " ms, ";
if ((msStop - msStart) > 0)
std::cout << (perftcount/(msStop - msStart)) << " knods/s";
std::cout << std::endl;
CMD_BUFF_COUNT = '\0';
#ifdef WINGLET_DEBUG_PERFT
std::cout << "captures = " << ICAPT << std::endl;
std::cout << "en-passant = " << IEP << std::endl;
std::cout << "castlings = " << ICASTLOO + ICASTLOOO << std::endl;
std::cout << "promotions = " << IPROM << std::endl;
std::cout << "checks = " << ICHECK << std::endl;
#endif
return true;
}
// =================================================================
// r: rotate board
// =================================================================
if (!strcmp(buf, "r"))
{
board.viewRotated = !board.viewRotated;
board.display();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// readfen filename n : reads #-th FEN position from filename
// =================================================================
if (!strncmp(buf, "readfen", 7))
{
sscanf(buf+7,"%s %d", userinput, &number);
board.init();
readFen(userinput, number);
board.display();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// sd n: set the search depth to n
// =================================================================
if (!strncmp(buf, "sd", 2))
{
sscanf(buf+2,"%d", &board.searchDepth);
std::cout << "winglet> search depth " << board.searchDepth << std::endl;
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// setup : setup board...
// =================================================================
if (!strncmp(buf, "setup", 5))
{
setup();
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// undo: take back last move
// =================================================================
if (!strcmp(buf, "undo"))
{
if (board.endOfGame)
{
unmakeMove(board.gameLine[--board.endOfGame].move);
board.endOfSearch = board.endOfGame;
board.display();
}
else
{
std::cout << "already at start of game" << std::endl;
}
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// white: white to move
// =================================================================
if (!strcmp(buf, "white"))
{
board.nextMove = WHITE_MOVE;
CMD_BUFF_COUNT = '\0';
return true;
}
// =================================================================
// unknown command
// =================================================================
std::cout << " command not implemented: " << buf << ", type 'help' for more info" << std::endl;
CMD_BUFF_COUNT = '\0';
return true;
}
There still are some serious issues with the current search
functionality, we will address these one by one in the next sections.
The most important shortcomings are:
-
the search assumes that there will always be a legal move. Of course that is not true in case one of the variations leads to a stalemate, or a checkmate, before the end of the tree is reached. Checkmates are not identified a such !
-
there is no move ordering, which makes the search still kind of sluggish, and doing a lot of unnecessary work.
-
you will often see a score that is oscillating for even/odd search depths (high for odd search depths, low for even search depths), and the last move in the PV is a capture. This is because we are searching to a fixed depth and then stop, even if we are in the middle of an exchange of pieces. Actually, since there is no check for this, the search will now show a preference to end the PV with a capture for the side to move (or promotion), because the side not to move cannot recapture!
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last update: Sunday 19 June 2011