diff options
Diffstat (limited to 'ver3/ttt.c')
| -rw-r--r-- | ver3/ttt.c | 1550 |
1 files changed, 775 insertions, 775 deletions
@@ -1,775 +1,775 @@ -/*++
-
-Module Name:
-
- ttt.c
-
-Abstract:
-
- tic tac toe program to illustrate simple minimax searching
-
-Author:
-
- Scott Gasch (SGasch) 18 Mar 2004
-
-Revision History:
-
- ver0 : random play
- ver1 : simple search
- ver2 : alpha beta search
- ver3 : added eval and depth on ab search, more efficient gaveover
-
---*/
-
-#include <stdlib.h>
-#include <stdio.h>
-#include <memory.h>
-#include <time.h>
-#include "ttt.h"
-
-SQUARE g_sComputerPlays = O_MARK; // what side comp plays
-unsigned int g_uPly = 0;
-MOVE g_mvBest = { 0 };
-unsigned int g_uNodes = 0;
-
-//+----------------------------------------------------------------------------
-//
-// Function: SquareContentsToChar
-//
-// Synopsis: Helper function for DrawBoard
-//
-// Arguments: IN SQUARE s - a square to return a char to represent
-//
-// Returns: char - character representing square
-//
-//+----------------------------------------------------------------------------
-char SquareContentsToChar(IN SQUARE s)
-{
- static char c;
- switch(s)
- {
- case X_MARK:
- c = 'X';
- break;
- case O_MARK:
- c = 'O';
- break;
- case EMPTY:
- c = '_';
- break;
- default:
- ASSERT(FALSE);
- c = '?';
- break;
- }
- return(c);
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: DrawBoard
-//
-// Synopsis: Draw the board
-//
-// Arguments: IN POSITION *p - pointer to a position whose board to draw
-//
-// Returns: void
-//
-//+----------------------------------------------------------------------------
-void DrawBoard(IN POSITION *p)
-{
- COORD x, y;
-
- for (y = 0; y < BOARD_SIZE; y++)
- {
- for (x = 0; x < BOARD_SIZE; x++)
- {
- printf("%c ", SquareContentsToChar(p->sBoard[y][x]));
- }
-#ifdef DEBUG
- printf(" = %d\n", p->iHSums[y]);
-#else
- printf("\n");
-#endif
- }
-
-#ifdef DEBUG
- for (x = 0; x < BOARD_SIZE; x++)
- {
- printf("| ");
- }
- printf("\n");
- for (x = 0; x < BOARD_SIZE; x++)
- {
- printf("%d ", p->iVSums[x]);
- }
- printf("\n");
-#endif
-
- ASSERT(X_OR_O(p->sWhoseTurn));
- printf("\n%c to move.\n", SquareContentsToChar(p->sWhoseTurn));
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: ClearBoard
-//
-// Synopsis: Clear the board
-//
-// Arguments: IN OUT POSITION *p - pointer to position whose board to clear
-//
-// Returns: void
-//
-//+----------------------------------------------------------------------------
-void ClearBoard(IN OUT POSITION *p)
-{
- memset(p->sBoard, 0, sizeof(p->sBoard));
- memset(p->iHSums, 0, sizeof(p->iHSums));
- memset(p->iVSums, 0, sizeof(p->iVSums));
- p->iDSums[0] = p->iDSums[1] = 0;
- p->sWhoseTurn = X_MARK; // x's go first
- p->uNumEmpty = (BOARD_SIZE * BOARD_SIZE);
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: IsLegalMove
-//
-// Synopsis: Determine if a given move is legal on a given board
-//
-// Arguments: IN POSITION *p - the board to play the move on
-// IN MOVE *m - the move in question
-//
-// Returns: BOOL - TRUE if it's legal, FALSE otherwise
-//
-//+----------------------------------------------------------------------------
-BOOL IsLegalMove(IN POSITION *p, IN MOVE *m)
-{
- if ((m->cVpos < BOARD_SIZE) && (m->cHpos < BOARD_SIZE))
- {
- if (IS_SQUARE_EMPTY(p->sBoard[m->cVpos][m->cHpos]))
- {
- return(TRUE);
- }
- }
- return(FALSE);
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: GetHumanMove
-//
-// Synopsis: Ask the human for a move
-//
-// Arguments: IN POSITION *p - the current board
-// OUT MOVE *m - the move the human made; this struct is populated
-// as a side-effect of this function.
-//
-// Returns: void* (populates the move struct)
-//
-//+----------------------------------------------------------------------------
-void GetHumanMove(IN POSITION *p, OUT MOVE *m)
-{
- unsigned int x;
-
- do
- {
- printf("Enter your move number: ");
- scanf("%u", &x);
-
- m->cHpos = NUM_TO_HPOS(x);
- m->cVpos = NUM_TO_VPOS(x);
- m->sMark = OPPOSITE_MARK(g_sComputerPlays);
- }
- while(FALSE == IsLegalMove(p, m));
-}
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: GameOver
-//
-// Synopsis: Is the game over?
-//
-// Arguments: IN POSITION *p - the board
-// OUT SQUARE *psWhoWon - who won the game (if it's over)
-//
-// Returns: TRUE if the game is over. Also sets psWhoWon telling
-// which side one if the game is over. This also serves
-// as a very simple evaluation routine for the search.
-//
-// FALSE if the game is not over.
-//
-//+----------------------------------------------------------------------------
-BOOL GameOver(IN POSITION *p, OUT SQUARE *psWhoWon)
-{
- int iSum;
- COORD x;
-
- for (x = 0; x < BOARD_SIZE; x++)
- {
- iSum = p->iHSums[x];
- if (abs(iSum) == BOARD_SIZE) goto winner;
-
- iSum = p->iVSums[x];
- if (abs(iSum) == BOARD_SIZE) goto winner;
- }
-
- iSum = p->iDSums[0];
- if (abs(iSum) == BOARD_SIZE) goto winner;
-
- iSum = p->iDSums[1];
- if (abs(iSum) == BOARD_SIZE) goto winner;
-
- //
- // No one won yet, either game ongoing or draw.
- //
- *psWhoWon = EMPTY;
- if (p->uNumEmpty == 0)
- {
- return(TRUE);
- }
- else
- {
- return(FALSE);
- }
-
- winner:
- //
- // Some side won
- //
- *psWhoWon = (iSum / BOARD_SIZE);
- ASSERT(X_OR_O(*psWhoWon));
- return(TRUE);
-}
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: CountAdjacents
-//
-// Synopsis: Return the number of marks in adjacent squares to square x
-// that are of the same type (x or o) as the mark in square x.
-//
-// FIXME: does not consider diagonals
-//
-// Arguments: IN POSITION *p - the board
-// IN SQUARE x - the square to test
-//
-// Returns: A count
-//
-//+----------------------------------------------------------------------------
-unsigned int CountAdjacents(IN POSITION *p, IN SQUARE x)
-{
- COORD v = NUM_TO_VPOS(x);
- COORD h = NUM_TO_HPOS(x);
- SQUARE sSide = p->sBoard[h][v];
- unsigned int uCount = 0;
-
- //
- // If nothing at square x, nothing to count
- //
- if (sSide == EMPTY) goto end;
-
- //
- // Look above, below, left and right
- //
- if ((v > 0) && (p->sBoard[h][v-1] == sSide))
- {
- uCount++;
- }
-
- if ((v < (BOARD_SIZE - 1)) && (p->sBoard[h][v+1] == sSide))
- {
- uCount++;
- }
-
- if ((h > 0) && (p->sBoard[h-1][v] == sSide))
- {
- uCount++;
- }
-
- if ((h < (BOARD_SIZE - 1)) && (p->sBoard[h+1][v] == sSide))
- {
- uCount++;
- }
-
- end:
- ASSERT(0 <= uCount);
- ASSERT(uCount <= 4);
- return(uCount);
-}
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: Eval
-//
-// Synopsis: Evaluate a position
-//
-// Arguments: IN POSITION *p - the board
-//
-// Returns: A score
-//
-//+----------------------------------------------------------------------------
-int Eval(IN POSITION *p)
-{
- SQUARE sWinner;
- COORD x;
- SQUARE sMark;
- int iScore = 0;
-
- //
- // See if the game is already over.
- //
- if (TRUE == GameOver(p, &sWinner))
- {
- if (sWinner == p->sWhoseTurn)
- {
- iScore = +INFINITY - g_uPly;
- goto end;
- }
- else if (sWinner == OPPOSITE_MARK(p->sWhoseTurn))
- {
- iScore = -INFINITY + g_uPly;
- goto end;
- }
- iScore = DRAWSCORE;
- goto end;
- }
-
- //
- // No one won but instead of returning score=0 see if we can
- // find some "good characteristics" or "bad characteristics"
- // of the position and give bonuses / penalties.
- //
- for (x = BOARD_SIZE + 1;
- x < ((BOARD_SIZE * BOARD_SIZE) - BOARD_SIZE - 1);
- x++)
- {
- sMark = p->sBoard[NUM_TO_HPOS(x)][NUM_TO_VPOS(x)];
- if (sMark == p->sWhoseTurn)
- {
- iScore += CountAdjacents(p, x);
- }
- else if (sMark == OPPOSITE_MARK(p->sWhoseTurn))
- {
- iScore -= CountAdjacents(p, x);
- }
- }
-
- end:
- ASSERT(-INFINITY <= iScore);
- ASSERT(iScore <= +INFINITY);
- return(iScore);
-}
-
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: MakeMove
-//
-// Synopsis: Make a move on a board
-//
-// Arguments: IN OUT POSITION *p - the board
-// IN MOVE *m - the move
-//
-// Returns: void
-//
-//+----------------------------------------------------------------------------
-void MakeMove(IN OUT POSITION *p, IN MOVE *m)
-{
- if (TRUE == IsLegalMove(p, m))
- {
- //
- // Make the new make on the board
- //
- ASSERT(p->sBoard[m->cVpos][m->cHpos] == EMPTY);
- p->sBoard[m->cVpos][m->cHpos] = m->sMark;
-
- //
- // One less empty square
- //
- p->uNumEmpty--;
- ASSERT(p->uNumEmpty < (BOARD_SIZE * BOARD_SIZE));
-
- //
- // Update sums as appropriate
- //
- p->iHSums[m->cHpos] += m->sMark;
- ASSERT(VALID_SUM(p->iHSums[m->cHpos]));
- p->iVSums[m->cVpos] += m->sMark;
- ASSERT(VALID_SUM(p->iVSums[m->cVpos]));
- if (m->cHpos == m->cVpos)
- {
- p->iDSums[0] += m->sMark;
- ASSERT(VALID_SUM(p->iDSums[0]));
- }
- else if (m->cHpos == (BOARD_SIZE - m->cVpos))
- {
- p->iDSums[1] += m->sMark;
- ASSERT(VALID_SUM(p->iDSums[1]));
- }
-
- //
- // Other guy's turn
- //
- p->sWhoseTurn = OPPOSITE_MARK(p->sWhoseTurn);
- ASSERT(X_OR_O(p->sWhoseTurn));
-
- //
- // One ply deeper
- //
- g_uPly++;
- ASSERT(g_uPly > 0);
- }
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: UnmakeMove
-//
-// Synopsis: The opposite of MakeMove
-//
-// Arguments: IN OUT POSITION *p - the board
-// IN MOVE *m - the move to undo
-//
-// Returns: void
-//
-//+----------------------------------------------------------------------------
-void UnmakeMove(IN OUT POSITION *p, IN MOVE *m)
-{
- if (p->sBoard[m->cVpos][m->cHpos] == m->sMark)
- {
- p->sBoard[m->cVpos][m->cHpos] = EMPTY;
-
- //
- // One more empty square
- //
- p->uNumEmpty++;
- ASSERT(p->uNumEmpty > 0);
- ASSERT(p->uNumEmpty <= (BOARD_SIZE * BOARD_SIZE));
-
- //
- // Update sums as appropriate
- //
- p->iHSums[m->cHpos] -= m->sMark;
- ASSERT(VALID_SUM(p->iHSums[m->cHpos]));
- p->iVSums[m->cVpos] -= m->sMark;
- ASSERT(VALID_SUM(p->iVSums[m->cVpos]));
- if (m->cHpos == m->cVpos)
- {
- p->iDSums[0] -= m->sMark;
- ASSERT(VALID_SUM(p->iDSums[0]));
- }
- else if (m->cHpos == (BOARD_SIZE - m->cVpos))
- {
- p->iDSums[1] -= m->sMark;
- ASSERT(VALID_SUM(p->iDSums[1]));
- }
-
- //
- // Other guy's turn
- //
- p->sWhoseTurn = OPPOSITE_MARK(p->sWhoseTurn);
- ASSERT(X_OR_O(p->sWhoseTurn));
-
- //
- // One ply deeper
- //
- ASSERT(g_uPly > 0);
- g_uPly--;
- }
-}
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: AlphaBeta
-//
-// Synopsis: An AlphaBeta Search
-//
-// Arguments: IN OUT POSITION *p - the board
-// IN int iAlpha - the lower bound of the score window
-// IN int iBeta - the upper bound of the score window
-// IN int uDepth - search depth horizon
-//
-// Returns: int
-//
-//+----------------------------------------------------------------------------
-int
-AlphaBeta(IN POSITION *p, IN int iAlpha, IN int iBeta, IN unsigned int uDepth)
-{
- SQUARE sWhoWon;
- SQUARE s;
- MOVE mv;
- int iScore;
- int iBestScore = -INFINITY;
-
- g_uNodes++;
-
- //
- // Evaluate this position
- //
- if (TRUE == GameOver(p, &sWhoWon))
- {
- if (sWhoWon == p->sWhoseTurn)
- {
- return(+INFINITY - g_uPly);
- }
- else if (sWhoWon == (p->sWhoseTurn * -1))
- {
- return(-INFINITY + g_uPly);
- }
- return(DRAWSCORE);
- }
- else
- {
- if (uDepth == 0)
- {
- return(Eval(p));
- }
- }
-
- //
- // No one won, game is still going. Evaluate every
- // possible move from here.
- //
- ASSERT(p->uNumEmpty > 0);
- for (s = 0; s < (BOARD_SIZE * BOARD_SIZE); s++)
- {
- mv.cHpos = NUM_TO_HPOS(s);
- mv.cVpos = NUM_TO_VPOS(s);
- mv.sMark = p->sWhoseTurn;
-
- if (IsLegalMove(p, &mv))
- {
- MakeMove(p, &mv);
-
- iScore = -1 * AlphaBeta(p, -iBeta, -iAlpha, uDepth - 1);
- ASSERT(-INFINITY <= iScore);
- ASSERT(iScore <= +INFINITY);
-
- UnmakeMove(p, &mv);
-
- if (iScore >= iBeta)
- {
- return(iScore);
- }
-
- if (iScore > iBestScore)
- {
- iBestScore = iScore;
-
- if (iScore > iAlpha)
- {
- iAlpha = iScore;
-
- //
- // If this is the ply 0 move, remember it.
- //
- if (g_uPly == 0)
- {
- g_mvBest = mv;
- }
- }
- }
- }
- }
- return(iBestScore);
-}
-
-
-//+----------------------------------------------------------------------------
-//
-// Function: SimpleSearch
-//
-// Synopsis: A Simple Search
-//
-// Arguments: IN OUT POSITION *p - the board
-//
-// Returns: int
-//
-//+----------------------------------------------------------------------------
-int
-SimpleSearch(IN POSITION *p)
-{
- SQUARE sWhoWon;
- SQUARE s;
- MOVE mv;
- int iScore;
- int iBestScore = -INFINITY;
-
- g_uNodes++;
-
- //
- // Evaluate this position
- //
- if (TRUE == GameOver(p, &sWhoWon))
- {
- if (sWhoWon == p->sWhoseTurn)
- {
- return(+INFINITY - g_uPly);
- }
- else if (sWhoWon == (p->sWhoseTurn * -1))
- {
- return(-INFINITY + g_uPly);
- }
- return(DRAWSCORE);
- }
-
- //
- // No one won, game is still going. Evaluate every
- // possible move from here.
- //
- ASSERT(p->uNumEmpty > 0);
- for (s = 0; s < (BOARD_SIZE * BOARD_SIZE); s++)
- {
- mv.cHpos = NUM_TO_HPOS(s);
- mv.cVpos = NUM_TO_VPOS(s);
- mv.sMark = p->sWhoseTurn;
-
- if (IsLegalMove(p, &mv))
- {
- MakeMove(p, &mv);
-
- iScore = -1 * SimpleSearch(p);
- if (iScore > iBestScore)
- {
- iBestScore = iScore;
- if (g_uPly == 1)
- {
- g_mvBest = mv;
- }
- }
- UnmakeMove(p, &mv);
- }
- }
- return(iBestScore);
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: SearchForComputerMove
-//
-// Synopsis: Use our sophisticated search algorithm to find a computer
-// move
-//
-// Arguments: IN POSITION *p - the current board
-// OUT MOVE *m - the move the computer chooses; this move struct
-// is populated as a side-effect of this function.
-//
-// Returns: void* (populates move struct)
-//
-//+----------------------------------------------------------------------------
-void SearchForComputerMove(IN POSITION *p, OUT MOVE *m)
-{
- unsigned int x;
-
-#if defined(PLAY_RANDOMLY)
-
- do
- {
- x = rand() % (BOARD_SIZE * BOARD_SIZE);
- m->cHpos = NUM_TO_HPOS(x);
- m->cVpos = NUM_TO_VPOS(x);
- m->sMark = g_sComputerPlays;
- }
- while(FALSE == IsLegalMove(p, m));
-
-#elif defined(SIMPLE_SEARCH)
-
- g_uPly = g_uNodes = 0;
- SimpleSearch(p);
- *m = g_mvBest;
- printf("Searched %u node(s).\n", g_uNodes);
-
-#elif defined(ALPHA_BETA_SEARCH)
-
- g_uPly = g_uNodes = 0;
- AlphaBeta(p, -INFINITY-1, +INFINITY+1, BOARD_SIZE);
- *m = g_mvBest;
- printf("Searched %u node(s).\n", g_uNodes);
-
-#else
-
- #error "No Search Strategy Defined"
-
-#endif
-}
-
-//+----------------------------------------------------------------------------
-//
-// Function: main
-//
-// Synopsis: The program entry point and main game loop.
-//
-// Arguments: void
-//
-// Returns: int
-//
-//+----------------------------------------------------------------------------
-int main(void)
-{
- POSITION p;
- MOVE mv;
- SQUARE sResult;
-
- //
- // Randomize: the random numbers returned by rand() will be based on
- // the system clock when the program starts up.
- //
- srand(time(0));
-
- //
- // Setup the board and draw it once.
- //
- ClearBoard(&p);
- DrawBoard(&p);
-
- //
- // Main game loop
- //
- do
- {
- //
- // See whose turn it is -- the human's or the computers -- and
- // get a move from whoever's turn it is.
- //
- if (p.sWhoseTurn == g_sComputerPlays)
- {
- SearchForComputerMove(&p, &mv);
- }
- else
- {
- GetHumanMove(&p, &mv);
- }
-
- //
- // Make the move on the board and draw the board again.
- //
- MakeMove(&p, &mv);
- DrawBoard(&p);
- }
- while(FALSE == GameOver(&p, &sResult));
-
- //
- // If we get here the game is over... see what happened.
- //
- switch(sResult)
- {
- case X_MARK:
- printf("\nX's win.\n");
- break;
- case O_MARK:
- printf("\nO's win.\n");
- break;
- default:
- printf("Tie (what a surprise)\n");
- break;
- }
-
- exit(0);
-}
-
+/*++ + +Module Name: + + ttt.c + +Abstract: + + tic tac toe program to illustrate simple minimax searching + +Author: + + Scott Gasch (SGasch) 18 Mar 2004 + +Revision History: + + ver0 : random play + ver1 : simple search + ver2 : alpha beta search + ver3 : added eval and depth on ab search, more efficient gaveover + +--*/ + +#include <stdlib.h> +#include <stdio.h> +#include <memory.h> +#include <time.h> +#include "ttt.h" + +SQUARE g_sComputerPlays = O_MARK; // what side comp plays +unsigned int g_uPly = 0; +MOVE g_mvBest = { 0 }; +unsigned int g_uNodes = 0; + +//+---------------------------------------------------------------------------- +// +// Function: SquareContentsToChar +// +// Synopsis: Helper function for DrawBoard +// +// Arguments: IN SQUARE s - a square to return a char to represent +// +// Returns: char - character representing square +// +//+---------------------------------------------------------------------------- +char SquareContentsToChar(IN SQUARE s) +{ + static char c; + switch(s) + { + case X_MARK: + c = 'X'; + break; + case O_MARK: + c = 'O'; + break; + case EMPTY: + c = '_'; + break; + default: + ASSERT(FALSE); + c = '?'; + break; + } + return(c); +} + +//+---------------------------------------------------------------------------- +// +// Function: DrawBoard +// +// Synopsis: Draw the board +// +// Arguments: IN POSITION *p - pointer to a position whose board to draw +// +// Returns: void +// +//+---------------------------------------------------------------------------- +void DrawBoard(IN POSITION *p) +{ + COORD x, y; + + for (y = 0; y < BOARD_SIZE; y++) + { + for (x = 0; x < BOARD_SIZE; x++) + { + printf("%c ", SquareContentsToChar(p->sBoard[y][x])); + } +#ifdef DEBUG + printf(" = %d\n", p->iHSums[y]); +#else + printf("\n"); +#endif + } + +#ifdef DEBUG + for (x = 0; x < BOARD_SIZE; x++) + { + printf("| "); + } + printf("\n"); + for (x = 0; x < BOARD_SIZE; x++) + { + printf("%d ", p->iVSums[x]); + } + printf("\n"); +#endif + + ASSERT(X_OR_O(p->sWhoseTurn)); + printf("\n%c to move.\n", SquareContentsToChar(p->sWhoseTurn)); +} + +//+---------------------------------------------------------------------------- +// +// Function: ClearBoard +// +// Synopsis: Clear the board +// +// Arguments: IN OUT POSITION *p - pointer to position whose board to clear +// +// Returns: void +// +//+---------------------------------------------------------------------------- +void ClearBoard(IN OUT POSITION *p) +{ + memset(p->sBoard, 0, sizeof(p->sBoard)); + memset(p->iHSums, 0, sizeof(p->iHSums)); + memset(p->iVSums, 0, sizeof(p->iVSums)); + p->iDSums[0] = p->iDSums[1] = 0; + p->sWhoseTurn = X_MARK; // x's go first + p->uNumEmpty = (BOARD_SIZE * BOARD_SIZE); +} + +//+---------------------------------------------------------------------------- +// +// Function: IsLegalMove +// +// Synopsis: Determine if a given move is legal on a given board +// +// Arguments: IN POSITION *p - the board to play the move on +// IN MOVE *m - the move in question +// +// Returns: BOOL - TRUE if it's legal, FALSE otherwise +// +//+---------------------------------------------------------------------------- +BOOL IsLegalMove(IN POSITION *p, IN MOVE *m) +{ + if ((m->cVpos < BOARD_SIZE) && (m->cHpos < BOARD_SIZE)) + { + if (IS_SQUARE_EMPTY(p->sBoard[m->cVpos][m->cHpos])) + { + return(TRUE); + } + } + return(FALSE); +} + +//+---------------------------------------------------------------------------- +// +// Function: GetHumanMove +// +// Synopsis: Ask the human for a move +// +// Arguments: IN POSITION *p - the current board +// OUT MOVE *m - the move the human made; this struct is populated +// as a side-effect of this function. +// +// Returns: void* (populates the move struct) +// +//+---------------------------------------------------------------------------- +void GetHumanMove(IN POSITION *p, OUT MOVE *m) +{ + unsigned int x; + + do + { + printf("Enter your move number: "); + scanf("%u", &x); + + m->cHpos = NUM_TO_HPOS(x); + m->cVpos = NUM_TO_VPOS(x); + m->sMark = OPPOSITE_MARK(g_sComputerPlays); + } + while(FALSE == IsLegalMove(p, m)); +} + + +//+---------------------------------------------------------------------------- +// +// Function: GameOver +// +// Synopsis: Is the game over? +// +// Arguments: IN POSITION *p - the board +// OUT SQUARE *psWhoWon - who won the game (if it's over) +// +// Returns: TRUE if the game is over. Also sets psWhoWon telling +// which side one if the game is over. This also serves +// as a very simple evaluation routine for the search. +// +// FALSE if the game is not over. +// +//+---------------------------------------------------------------------------- +BOOL GameOver(IN POSITION *p, OUT SQUARE *psWhoWon) +{ + int iSum; + COORD x; + + for (x = 0; x < BOARD_SIZE; x++) + { + iSum = p->iHSums[x]; + if (abs(iSum) == BOARD_SIZE) goto winner; + + iSum = p->iVSums[x]; + if (abs(iSum) == BOARD_SIZE) goto winner; + } + + iSum = p->iDSums[0]; + if (abs(iSum) == BOARD_SIZE) goto winner; + + iSum = p->iDSums[1]; + if (abs(iSum) == BOARD_SIZE) goto winner; + + // + // No one won yet, either game ongoing or draw. + // + *psWhoWon = EMPTY; + if (p->uNumEmpty == 0) + { + return(TRUE); + } + else + { + return(FALSE); + } + + winner: + // + // Some side won + // + *psWhoWon = (iSum / BOARD_SIZE); + ASSERT(X_OR_O(*psWhoWon)); + return(TRUE); +} + + +//+---------------------------------------------------------------------------- +// +// Function: CountAdjacents +// +// Synopsis: Return the number of marks in adjacent squares to square x +// that are of the same type (x or o) as the mark in square x. +// +// FIXME: does not consider diagonals +// +// Arguments: IN POSITION *p - the board +// IN SQUARE x - the square to test +// +// Returns: A count +// +//+---------------------------------------------------------------------------- +unsigned int CountAdjacents(IN POSITION *p, IN SQUARE x) +{ + COORD v = NUM_TO_VPOS(x); + COORD h = NUM_TO_HPOS(x); + SQUARE sSide = p->sBoard[h][v]; + unsigned int uCount = 0; + + // + // If nothing at square x, nothing to count + // + if (sSide == EMPTY) goto end; + + // + // Look above, below, left and right + // + if ((v > 0) && (p->sBoard[h][v-1] == sSide)) + { + uCount++; + } + + if ((v < (BOARD_SIZE - 1)) && (p->sBoard[h][v+1] == sSide)) + { + uCount++; + } + + if ((h > 0) && (p->sBoard[h-1][v] == sSide)) + { + uCount++; + } + + if ((h < (BOARD_SIZE - 1)) && (p->sBoard[h+1][v] == sSide)) + { + uCount++; + } + + end: + ASSERT(0 <= uCount); + ASSERT(uCount <= 4); + return(uCount); +} + + +//+---------------------------------------------------------------------------- +// +// Function: Eval +// +// Synopsis: Evaluate a position +// +// Arguments: IN POSITION *p - the board +// +// Returns: A score +// +//+---------------------------------------------------------------------------- +int Eval(IN POSITION *p) +{ + SQUARE sWinner; + COORD x; + SQUARE sMark; + int iScore = 0; + + // + // See if the game is already over. + // + if (TRUE == GameOver(p, &sWinner)) + { + if (sWinner == p->sWhoseTurn) + { + iScore = +INFINITY - g_uPly; + goto end; + } + else if (sWinner == OPPOSITE_MARK(p->sWhoseTurn)) + { + iScore = -INFINITY + g_uPly; + goto end; + } + iScore = DRAWSCORE; + goto end; + } + + // + // No one won but instead of returning score=0 see if we can + // find some "good characteristics" or "bad characteristics" + // of the position and give bonuses / penalties. + // + for (x = BOARD_SIZE + 1; + x < ((BOARD_SIZE * BOARD_SIZE) - BOARD_SIZE - 1); + x++) + { + sMark = p->sBoard[NUM_TO_HPOS(x)][NUM_TO_VPOS(x)]; + if (sMark == p->sWhoseTurn) + { + iScore += CountAdjacents(p, x); + } + else if (sMark == OPPOSITE_MARK(p->sWhoseTurn)) + { + iScore -= CountAdjacents(p, x); + } + } + + end: + ASSERT(-INFINITY <= iScore); + ASSERT(iScore <= +INFINITY); + return(iScore); +} + + + +//+---------------------------------------------------------------------------- +// +// Function: MakeMove +// +// Synopsis: Make a move on a board +// +// Arguments: IN OUT POSITION *p - the board +// IN MOVE *m - the move +// +// Returns: void +// +//+---------------------------------------------------------------------------- +void MakeMove(IN OUT POSITION *p, IN MOVE *m) +{ + if (TRUE == IsLegalMove(p, m)) + { + // + // Make the new make on the board + // + ASSERT(p->sBoard[m->cVpos][m->cHpos] == EMPTY); + p->sBoard[m->cVpos][m->cHpos] = m->sMark; + + // + // One less empty square + // + p->uNumEmpty--; + ASSERT(p->uNumEmpty < (BOARD_SIZE * BOARD_SIZE)); + + // + // Update sums as appropriate + // + p->iHSums[m->cHpos] += m->sMark; + ASSERT(VALID_SUM(p->iHSums[m->cHpos])); + p->iVSums[m->cVpos] += m->sMark; + ASSERT(VALID_SUM(p->iVSums[m->cVpos])); + if (m->cHpos == m->cVpos) + { + p->iDSums[0] += m->sMark; + ASSERT(VALID_SUM(p->iDSums[0])); + } + else if (m->cHpos == (BOARD_SIZE - m->cVpos)) + { + p->iDSums[1] += m->sMark; + ASSERT(VALID_SUM(p->iDSums[1])); + } + + // + // Other guy's turn + // + p->sWhoseTurn = OPPOSITE_MARK(p->sWhoseTurn); + ASSERT(X_OR_O(p->sWhoseTurn)); + + // + // One ply deeper + // + g_uPly++; + ASSERT(g_uPly > 0); + } +} + +//+---------------------------------------------------------------------------- +// +// Function: UnmakeMove +// +// Synopsis: The opposite of MakeMove +// +// Arguments: IN OUT POSITION *p - the board +// IN MOVE *m - the move to undo +// +// Returns: void +// +//+---------------------------------------------------------------------------- +void UnmakeMove(IN OUT POSITION *p, IN MOVE *m) +{ + if (p->sBoard[m->cVpos][m->cHpos] == m->sMark) + { + p->sBoard[m->cVpos][m->cHpos] = EMPTY; + + // + // One more empty square + // + p->uNumEmpty++; + ASSERT(p->uNumEmpty > 0); + ASSERT(p->uNumEmpty <= (BOARD_SIZE * BOARD_SIZE)); + + // + // Update sums as appropriate + // + p->iHSums[m->cHpos] -= m->sMark; + ASSERT(VALID_SUM(p->iHSums[m->cHpos])); + p->iVSums[m->cVpos] -= m->sMark; + ASSERT(VALID_SUM(p->iVSums[m->cVpos])); + if (m->cHpos == m->cVpos) + { + p->iDSums[0] -= m->sMark; + ASSERT(VALID_SUM(p->iDSums[0])); + } + else if (m->cHpos == (BOARD_SIZE - m->cVpos)) + { + p->iDSums[1] -= m->sMark; + ASSERT(VALID_SUM(p->iDSums[1])); + } + + // + // Other guy's turn + // + p->sWhoseTurn = OPPOSITE_MARK(p->sWhoseTurn); + ASSERT(X_OR_O(p->sWhoseTurn)); + + // + // One ply deeper + // + ASSERT(g_uPly > 0); + g_uPly--; + } +} + + +//+---------------------------------------------------------------------------- +// +// Function: AlphaBeta +// +// Synopsis: An AlphaBeta Search +// +// Arguments: IN OUT POSITION *p - the board +// IN int iAlpha - the lower bound of the score window +// IN int iBeta - the upper bound of the score window +// IN int uDepth - search depth horizon +// +// Returns: int +// +//+---------------------------------------------------------------------------- +int +AlphaBeta(IN POSITION *p, IN int iAlpha, IN int iBeta, IN unsigned int uDepth) +{ + SQUARE sWhoWon; + SQUARE s; + MOVE mv; + int iScore; + int iBestScore = -INFINITY; + + g_uNodes++; + + // + // Evaluate this position + // + if (TRUE == GameOver(p, &sWhoWon)) + { + if (sWhoWon == p->sWhoseTurn) + { + return(+INFINITY - g_uPly); + } + else if (sWhoWon == (p->sWhoseTurn * -1)) + { + return(-INFINITY + g_uPly); + } + return(DRAWSCORE); + } + else + { + if (uDepth == 0) + { + return(Eval(p)); + } + } + + // + // No one won, game is still going. Evaluate every + // possible move from here. + // + ASSERT(p->uNumEmpty > 0); + for (s = 0; s < (BOARD_SIZE * BOARD_SIZE); s++) + { + mv.cHpos = NUM_TO_HPOS(s); + mv.cVpos = NUM_TO_VPOS(s); + mv.sMark = p->sWhoseTurn; + + if (IsLegalMove(p, &mv)) + { + MakeMove(p, &mv); + + iScore = -1 * AlphaBeta(p, -iBeta, -iAlpha, uDepth - 1); + ASSERT(-INFINITY <= iScore); + ASSERT(iScore <= +INFINITY); + + UnmakeMove(p, &mv); + + if (iScore >= iBeta) + { + return(iScore); + } + + if (iScore > iBestScore) + { + iBestScore = iScore; + + if (iScore > iAlpha) + { + iAlpha = iScore; + + // + // If this is the ply 0 move, remember it. + // + if (g_uPly == 0) + { + g_mvBest = mv; + } + } + } + } + } + return(iBestScore); +} + + +//+---------------------------------------------------------------------------- +// +// Function: SimpleSearch +// +// Synopsis: A Simple Search +// +// Arguments: IN OUT POSITION *p - the board +// +// Returns: int +// +//+---------------------------------------------------------------------------- +int +SimpleSearch(IN POSITION *p) +{ + SQUARE sWhoWon; + SQUARE s; + MOVE mv; + int iScore; + int iBestScore = -INFINITY; + + g_uNodes++; + + // + // Evaluate this position + // + if (TRUE == GameOver(p, &sWhoWon)) + { + if (sWhoWon == p->sWhoseTurn) + { + return(+INFINITY - g_uPly); + } + else if (sWhoWon == (p->sWhoseTurn * -1)) + { + return(-INFINITY + g_uPly); + } + return(DRAWSCORE); + } + + // + // No one won, game is still going. Evaluate every + // possible move from here. + // + ASSERT(p->uNumEmpty > 0); + for (s = 0; s < (BOARD_SIZE * BOARD_SIZE); s++) + { + mv.cHpos = NUM_TO_HPOS(s); + mv.cVpos = NUM_TO_VPOS(s); + mv.sMark = p->sWhoseTurn; + + if (IsLegalMove(p, &mv)) + { + MakeMove(p, &mv); + + iScore = -1 * SimpleSearch(p); + if (iScore > iBestScore) + { + iBestScore = iScore; + if (g_uPly == 1) + { + g_mvBest = mv; + } + } + UnmakeMove(p, &mv); + } + } + return(iBestScore); +} + +//+---------------------------------------------------------------------------- +// +// Function: SearchForComputerMove +// +// Synopsis: Use our sophisticated search algorithm to find a computer +// move +// +// Arguments: IN POSITION *p - the current board +// OUT MOVE *m - the move the computer chooses; this move struct +// is populated as a side-effect of this function. +// +// Returns: void* (populates move struct) +// +//+---------------------------------------------------------------------------- +void SearchForComputerMove(IN POSITION *p, OUT MOVE *m) +{ + unsigned int x; + +#if defined(PLAY_RANDOMLY) + + do + { + x = rand() % (BOARD_SIZE * BOARD_SIZE); + m->cHpos = NUM_TO_HPOS(x); + m->cVpos = NUM_TO_VPOS(x); + m->sMark = g_sComputerPlays; + } + while(FALSE == IsLegalMove(p, m)); + +#elif defined(SIMPLE_SEARCH) + + g_uPly = g_uNodes = 0; + SimpleSearch(p); + *m = g_mvBest; + printf("Searched %u node(s).\n", g_uNodes); + +#elif defined(ALPHA_BETA_SEARCH) + + g_uPly = g_uNodes = 0; + AlphaBeta(p, -INFINITY-1, +INFINITY+1, BOARD_SIZE); + *m = g_mvBest; + printf("Searched %u node(s).\n", g_uNodes); + +#else + + #error "No Search Strategy Defined" + +#endif +} + +//+---------------------------------------------------------------------------- +// +// Function: main +// +// Synopsis: The program entry point and main game loop. +// +// Arguments: void +// +// Returns: int +// +//+---------------------------------------------------------------------------- +int main(void) +{ + POSITION p; + MOVE mv; + SQUARE sResult; + + // + // Randomize: the random numbers returned by rand() will be based on + // the system clock when the program starts up. + // + srand(time(0)); + + // + // Setup the board and draw it once. + // + ClearBoard(&p); + DrawBoard(&p); + + // + // Main game loop + // + do + { + // + // See whose turn it is -- the human's or the computers -- and + // get a move from whoever's turn it is. + // + if (p.sWhoseTurn == g_sComputerPlays) + { + SearchForComputerMove(&p, &mv); + } + else + { + GetHumanMove(&p, &mv); + } + + // + // Make the move on the board and draw the board again. + // + MakeMove(&p, &mv); + DrawBoard(&p); + } + while(FALSE == GameOver(&p, &sResult)); + + // + // If we get here the game is over... see what happened. + // + switch(sResult) + { + case X_MARK: + printf("\nX's win.\n"); + break; + case O_MARK: + printf("\nO's win.\n"); + break; + default: + printf("Tie (what a surprise)\n"); + break; + } + + exit(0); +} + |