games/backgammon/backgammon/extra.c

   1 /*
   2  * Copyright (c) 1980, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)extra.c  8.1 (Berkeley) 5/31/93
  34  * $FreeBSD: src/games/backgammon/backgammon/extra.c,v 1.4 1999/11/30 03:48:22 billf Exp $
  35  * $DragonFly: src/games/backgammon/backgammon/extra.c,v 1.3 2006/08/08 16:36:11 pavalos Exp $
  36  */
  37
  38 #include "back.h"
  39
  40 #ifdef DEBUG
  41 #include <stdio.h>
  42 FILE    *trace;
  43 #endif
  44
  45 static int      eval(void);
  46
  47 /*
  48  * dble()
  49  *      Have the current player double and ask opponent to accept.
  50  */
  51
  52 void
  53 dble(void)
  54 {
  55         int     resp;                   /* response to y/n */
  56
  57         for (;;)  {
  58                 writel (" doubles.");           /* indicate double */
  59
  60                 if (cturn == -pnum)  {          /* see if computer accepts */
  61                         if (dblgood())  {           /* guess not */
  62                                 writel ("  Declined.\n");
  63                                 nexturn();
  64                                 cturn *= -2;        /* indicate loss */
  65                                 return;
  66                         } else  {                   /* computer accepts */
  67                                 writel ("  Accepted.\n");
  68                                 gvalue *= 2;        /* double game value */
  69                                 dlast = cturn;
  70                                 if (tflag)
  71                                         gwrite();
  72                                 return;
  73                         }
  74                 }
  75
  76                                                 /* ask if player accepts */
  77                 writel ("  Does ");
  78                 writel (cturn == 1? color[2]: color[3]);
  79                 writel (" accept?");
  80
  81                                                 /* get response from yorn,
  82                                                  * a "2" means he said "p"
  83                                                  * for print board. */
  84                 if ((resp = yorn ('R')) == 2)  {
  85                         writel ("  Reprint.\n");
  86                         buflush();
  87                         wrboard();
  88                         writel (*Colorptr);
  89                         continue;
  90                 }
  91
  92                                                 /* check response */
  93                 if (resp)  {
  94                                                     /* accepted */
  95                         gvalue *= 2;
  96                         dlast = cturn;
  97                         if (tflag)
  98                                 gwrite();
  99                         return;
 100                 }
 101
 102                 nexturn ();                     /* declined */
 103                 cturn *= -2;
 104                 return;
 105         }
 106 }
 107
 108 /*
 109  * dblgood ()
 110  *      Returns 1 if the computer would double in this position.  This
 111  * is not an exact science.  The computer will decline a double that he
 112  * would have made.  Accumulated judgments are kept in the variable n,
 113  * which is in "pips", i.e., the position of each man summed over all
 114  * men, with opponent's totals negative.  Thus, n should have a positive
 115  * value of 7 for each move ahead, or a negative value of 7 for each one
 116  * behind.
 117  */
 118
 119 int
 120 dblgood(void)
 121 {
 122         int     n;                      /* accumulated judgment */
 123         int     OFFC = *offptr;         /* no. of computer's men off */
 124         int     OFFO = *offopp;         /* no. of player's men off */
 125
 126 #ifdef DEBUG
 127         int     i;
 128         if (trace == NULL)
 129                 trace = fopen ("bgtrace","w");
 130 #endif
 131
 132                                                 /* get real pip value */
 133         n = eval()*cturn;
 134 #ifdef DEBUG
 135         fputs ("\nDoubles:\nBoard: ",trace);
 136         for (i = 0; i < 26; i++)
 137                 fprintf (trace," %d",board[i]);
 138         fprintf (trace,"\n\tpip = %d, ",n);
 139 #endif
 140
 141                                                 /* below adjusts pip value
 142                                                  * according to position
 143                                                  * judgments */
 144
 145                                                 /* check men moving off
 146                                                  * board */
 147         if (OFFC > -15 || OFFO > -15)  {
 148                 if (OFFC < 0 && OFFO < 0)  {
 149                         OFFC += 15;
 150                         OFFO += 15;
 151                         n +=((OFFC-OFFO)*7)/2;
 152                 } else if (OFFC < 0)  {
 153                         OFFC += 15;
 154                         n -= OFFO*7/2;
 155                 } else if (OFFO < 0)  {
 156                         OFFO += 15;
 157                         n += OFFC*7/2;
 158                 }
 159                 if (OFFC < 8 && OFFO > 8)
 160                         n -= 7;
 161                 if (OFFC < 10 && OFFO > 10)
 162                         n -= 7;
 163                 if (OFFC < 12 && OFFO > 12)
 164                         n -= 7;
 165                 if (OFFO < 8 && OFFC > 8)
 166                         n += 7;
 167                 if (OFFO < 10 && OFFC > 10)
 168                         n += 7;
 169                 if (OFFO < 12 && OFFC > 12)
 170                         n += 7;
 171                 n += ((OFFC-OFFO)*7)/2;
 172         }
 173
 174 #ifdef DEBUG
 175         fprintf (trace,"off = %d, ",n);
 176 #endif
 177
 178                                                 /* see if men are trapped */
 179         n -= freemen(bar);
 180         n += freemen(home);
 181         n += trapped(home,-cturn);
 182         n -= trapped(bar,cturn);
 183
 184 #ifdef DEBUG
 185         fprintf (trace,"free = %d\n",n);
 186         fprintf (trace,"\tOFFC = %d, OFFO = %d\n",OFFC,OFFO);
 187         fflush (trace);
 188 #endif
 189
 190                                                 /* double if 2-3 moves ahead */
 191         if (n > 10+rnum(7))
 192                 return(1);
 193         return (0);
 194 }
 195
 196 int
 197 freemen(int b)
 198 {
 199         int             i, inc, lim;
 200
 201         odds(0,0,0);
 202         if (board[b] == 0)
 203                 return (0);
 204         inc = (b == 0? 1: -1);
 205         lim = (b == 0? 7: 18);
 206         for (i = b+inc; i != lim; i += inc)
 207                 if (board[i]*inc < -1)
 208                         odds(abs(b-i),0,abs(board[b]));
 209         if (abs(board[b]) == 1)
 210                 return ((36-count())/5);
 211         return (count()/5);
 212 }
 213
 214 int
 215 trapped(int n, int inc)
 216 {
 217         int             i, j, k;
 218         int             c, l, ct;
 219
 220         ct = 0;
 221         l = n+7*inc;
 222         for (i = n+inc; i != l; i += inc)  {
 223                 odds (0,0,0);
 224                 c = abs(i-l);
 225                 if (board[i]*inc > 0)  {
 226                         for (j = c; j < 13; j++)
 227                                 if (board[i+inc*j]*inc < -1)  {
 228                                         if (j < 7)
 229                                                 odds (j,0,1);
 230                                         for (k = 1; k < 7 && k < j; k++)
 231                                                 if (j-k < 7)
 232                                                         odds (k,j-k,1);
 233                                 }
 234                         ct += abs(board[i])*(36-count());
 235                 }
 236         }
 237         return (ct/5);
 238 }
 239
 240 static int
 241 eval(void)
 242 {
 243         int             i, j;
 244
 245         for (j = i = 0; i < 26; i++)
 246                 j += (board[i] >= 0 ? i*board[i] : (25-i)*board[i]);
 247
 248         if (off[1] >= 0)
 249                 j += 25*off[1];
 250         else
 251                 j += 25*(off[1]+15);
 252
 253         if (off[0] >= 0)
 254                 j -= 25*off[0];
 255         else
 256                 j -= 25*(off[0]+15);
 257         return (j);
 258 }