seval.c   [plain text]

/*
    Sjeng - a chess variants playing program
    Copyright (C) 2000 Gian-Carlo Pascutto

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    File: seval.c                                        
    Purpose: functions for evaluating positions (suicide chess)

*/

#include "sjeng.h"
#include "extvars.h"
#include "protos.h"

static int scentral[144] = {
0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,
0,0,-20,-10,-10,-10,-10,-10,-10,-20,0,0,
0,0,-10,0,3,5,5,3,0,-10,0,0,
0,0,-10,2,15,15,15,15,2,-10,0,0,
0,0,-10,7,15,25,25,15,7,-10,0,0,
0,0,-10,7,15,25,25,15,7,-10,0,0,
0,0,-10,2,15,15,15,15,2,-10,0,0,
0,0,-10,0,3,5,5,3,0,-10,0,0,
0,0,-20,-10,-10,-10,-10,-10,-10,-20,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0};

static const int rook_o[4] = {12, -12, 1, -1};
static const int bishop_o[4] = {11, -11, 13, -13};
static const int knight_o[8] = {10, -10, 14, -14, 23, -23, 25, -25};

static int s_bishop_mobility(int square)
{
  register int l;
  register int m = 0;

  for (l = square-13; board[l] == npiece; l-=13)
    m++;
  for (l = square-11; board[l] == npiece; l-=11)
    m++;
  for (l = square+11; board[l] == npiece; l+=11)
    m++;
  for (l = square+13; board[l] == npiece; l+=13)
    m++;
  
  return m << 2;
}

static int s_rook_mobility(int square)
{
  register int l;
  register int m = 0;

  for (l = square-12; board[l] == npiece; l-=12)
    m++;
  for (l = square-1; board[l] == npiece; l-=1)
    m++;
  for (l = square+1; board[l] == npiece; l+=1)
    m++;
  for (l = square+12; board[l] == npiece; l+=12)
    m++;
  
  return m << 2;
}

static int s_knight_mobility(int square)
{ 
  static const int knight_o[8] = {10, -10, 14, -14, 23, -23, 25, -25};
  register int d, m = 0;
  
  for (d = 0; d < 8; d++)
    {
      if (board[square + knight_o[d]] == npiece) m++;
    }
	
  return m << 2;
}

static int s_pawn_mobility(int square)
{
  register int m = 0;

  if (board[square] == wpawn)
    {
      if (board[square + 12] == npiece) m++;
    }
  else
    {
      if (board[square - 12] == npiece) m++;
    } 

  return m << 3;
}

static int s_king_mobility(int square)
{
  static const int king_o[8] = {13, 12, 11, 1, -1, -11, -12, -13};
  register int d, m = 0;
  
  for (d = 0; d < 8; d++)
    {
      if (board[square + king_o[d]] == npiece) m++;
    }

  return m << 2;
}

static int black_saccers(int square)
{
  register int ndir, a_sq;
  register int basq, i;
  register int f = FALSE;

  /* for white pawn on square, any black
   * pieces that can sac themselves to it? */
  
  /* check for case where is_attacked fails
     because pawns dont move to their attacks */
  
  if (board[square + 24] == bpawn ||
      board[square + 22] == bpawn ||
      board[square + 26] == bpawn)
    {
      return 0;
    }

  /* ok, now check pawn moves */

  if ((rank(square) < 6) 
      && (board[square + 25] == bpawn 
	  ||
	  board[square + 23] == bpawn))
    {
      f = TRUE;
    }
  else if (rank(square) == 4 &&
	   (board[square + 35] == bpawn ||
	   board[square + 37] == bpawn))
    {
      f = TRUE;
    }
  
  if (!f)
    {
      f = (is_attacked(square + 11, 0) ? 1 : 0);
    }
  if (!f)
    {
      f = (is_attacked(square + 13, 0) ? 2 : 0);
    }
  
  if (!f)
    {
      return 0;
    }
  else
    {
      /* black can sac, but is the saccer defended ? */
      
      if (f == 1)
	{
	  if (calc_attackers(square + 11, 0) > 1)
	    {
	      /* yep */
	      return 0;
	    }
	  else
	    {
	      /* nope */
	      return 30;
	    }
	}
      else
	{
	  if (calc_attackers(square + 13, 0) > 1)
	    {
	      return 0;
	    }
	  else
	    {
	      return 30;
	    }
	  
	}
    }
  
}

static int white_saccers(int square)
{
  /* for black pawn on square, any black
   * pieces that can sac themselves to it? */
  
  register int ndir, a_sq;
  register int basq, i;
  register int f = FALSE;

  /* for white pawn on square, any black
   * pieces that can sac themselves to it? */
  
  /* check for case where is_attacked fails
     because pawns dont move to their attacks */
  
  if (board[square - 24] == wpawn ||
      board[square - 22] == wpawn ||
      board[square - 26] == wpawn)
    {
      return 0;
    }

  /* ok, now check pawn moves */

  if ((rank(square) > 3) 
      && (board[square - 25] == wpawn 
	  ||
	  board[square - 23] == wpawn))
    {
      f = TRUE;
    }
  else if (rank(square) == 5 &&
	   (board[square - 35] == wpawn ||
	   board[square - 37] == wpawn))
    {
      f = TRUE;
    }
  
  if (!f)
    {
      f = (is_attacked(square - 11, 1) ? 1 : 0);
    }
  if (!f)
    {
      f = (is_attacked(square - 13, 1) ? 2 : 0);
    }
  
  if (!f)
    {
      return 0;
    }
  else
    {
      /* black can sac, but is the saccer defended ? */
      
      if (f == 1)
	{
	  if (calc_attackers(square - 11, 1) > 1)
	    {
	      /* yep */
	      return 0;
	    }
	  else
	    {
	      /* nope */
	      return 30;
	    }
	}
      else
	{
	  if (calc_attackers(square - 13, 1) > 1)
	    {
	      return 0;
	    }
	  else
	    {
	      return 30;
	    }
	  
	}
    }

}

int32_t suicide_eval (void) {

  /* select the appropriate eval() routine: */
  return (suicide_mid_eval ());
}

int32_t suicide_mid_eval (void) {

  /* return a score for the current middlegame position: */

  int srank, pawn_file, pawns[2][11], white_back_pawn[11], black_back_pawn[11];
  int isolated, backwards, i, a, j;
  int32_t score = 0;
  int in_cache;
  int wb = 0, bb = 0, wbc = 0, bbc = 0;
  int wk = 0, bk = 0, wr = 0, br = 0;
  int wn = 0, bn = 0, wp = 0, bp = 0;
  
  in_cache = 0;
  
  checkECache(&score, &in_cache);
  
  if(in_cache)
    {
      if (white_to_move == 1) return score;
      return -score;
    } 

  score = Material;

  /* initialize the pawns array, (files offset by one to use dummy files in
     order to easier determine isolated status) and also initialize the
     arrays keeping track of the rank of the most backward pawn: */
  memset (pawns, 0, sizeof (pawns));
  for (i = 0; i < 11; i++) {
    white_back_pawn[i] = 7;
    black_back_pawn[i] = 2;
  }
  for (j = 1, a = 1; (a <= piece_count); j++) {
     i = pieces[j];
    
    if (!i)
      continue;
    else
      a++;

    assert((i > 0) && (i < 145));
 
    pawn_file = file (i)+1;
    srank = rank (i);
    if (board[i] == wpawn) {
      pawns[1][pawn_file]++;
      if (srank < white_back_pawn[pawn_file]) {
	white_back_pawn[pawn_file] = srank;
      }
    }
    else if (board[i] == bpawn) {
      pawns[0][pawn_file]++;
      if (srank > black_back_pawn[pawn_file]) {
	black_back_pawn[pawn_file] = srank;
      }
    }
  }

  /* loop through the board, adding material value, as well as positional
     bonuses for all pieces encountered: */
  for (j = 1, a = 1; (a <= piece_count); j++) {
    i = pieces[j];
    
    if (!i)
      continue;
    else
      a++;

    pawn_file = file (i)+1;
    srank = rank (i);
    switch (board[i]) {
      case (wpawn):
	score += scentral[i];
	score += s_pawn_mobility(i);
        score -= black_saccers(i);
	wp++;
	isolated = FALSE;
	backwards = FALSE;
	
	/* check for backwards pawns: */
	if (white_back_pawn[pawn_file+1] > srank
	    && white_back_pawn[pawn_file-1] > srank) {
	  score -= 8;
	  backwards = TRUE;
	  /* check to see if it is furthermore isolated: */
	  if (!pawns[1][pawn_file+1] && !pawns[1][pawn_file-1]) {
	    score -= 12;
	    isolated = TRUE;
	  }
	}

	/* give weak, exposed pawns a penalty (not as much as in the midgame,
	   since there may be no pieces to take advantage of it): */
	if (!pawns[0][pawn_file]) {
	  if (backwards) score -= 5;
	  if (isolated) score -= 8;
	}

	/* give doubled, trippled, etc.. pawns a penalty (bigger in the
	   endgame, since they will become big targets): */
	if (pawns[1][pawn_file] > 1)
	  score -= 15*(pawns[1][pawn_file]-1);

	/* give bonuses for passed pawns (bigger in the endgame since passed
	   pawns are what wins the endgame): */
	if (!pawns[0][pawn_file] && srank >= black_back_pawn[pawn_file-1] &&
	    srank >= black_back_pawn[pawn_file+1]) {
	  score += 30 + 3*(rank(i)-2);

	  /* outside passer ? */
	  if (file(i) == 1 || file(i) == 8)
	    score += 4 + 2*(rank(i)-2);
	    
	  /* give an extra bonus if a connected, passed pawn: */
	  if (!isolated)
	    {
	      score += 6;
	    }
	}

	/* check for pawn islands */
	if (!pawns[1][pawn_file-1])
	  score -= 20;

	break;

     case (bpawn):
	score -= scentral[i];
	score -= s_pawn_mobility(i);
	score += white_saccers(i);
	isolated = FALSE;
	backwards = FALSE;
        bp++;
	
	/* in general, bonuses/penalties in the endgame evaluation will be
	   higher, since pawn structure becomes more important for the
	   creation of passed pawns */

	/* check for backwards pawns: */
	if (black_back_pawn[pawn_file+1] < srank
	    && black_back_pawn[pawn_file-1] < srank) {
	  score += 8;
	  backwards = TRUE;
	  /* check to see if it is furthermore isolated: */
	  if (!pawns[0][pawn_file+1] && !pawns[0][pawn_file-1]) {
	    score += 12;
	    isolated = TRUE;
	  }
	}

	/* give weak, exposed pawns a penalty (not as much as in the midgame,
	   since there may be no pieces to take advantage of it): */
	if (!pawns[1][pawn_file]) {
	  if (backwards) score += 5;
	  if (isolated) score += 8;
	}

	/* give doubled, trippled, etc.. pawns a penalty (bigger in the
	   endgame, since they will become big targets): */
	if (pawns[0][pawn_file] > 1)
	  score += 15*(pawns[0][pawn_file]-1);

	/* give bonuses for passed pawns (bigger in the endgame since passed
	   pawns are what wins the endgame): */
	if (!pawns[1][pawn_file] && srank <= white_back_pawn[pawn_file-1] &&
	    srank <= white_back_pawn[pawn_file+1]) {
	  score -= 30 + 3*(7-rank(i));
	      
	  /* outside passer ? */
	  if (file(i) == 1 || file(i) == 8)
	    score -= 4 + 2*(7-rank(i));
	  
	  /* give an extra bonus if a connected, passed pawn: */
	  if (!isolated)
	    {
	      score -= 6;
	    }
	}

	if (!pawns[0][pawn_file-1])
	  score += 20;

	break;

      case (wrook):
	score += scentral[i];
	score += s_rook_mobility(i);
	wr++;
	break;

      case (brook):
	score -= scentral[i];
	score -= s_rook_mobility(i);
	br++;
	break;

      case (wbishop):
	score += scentral[i];
	score += s_bishop_mobility(i);
	if (wb)
	{
	  if (sqcolor[i] != wbc)
	    wb = 99;
	}
	wb++;
	wbc = sqcolor[i];
	break;

      case (bbishop):
	score -= scentral[i];
	score -= s_bishop_mobility(i);
	if (bb) 
	{
	  /* two bishops, check for same color */
          if (sqcolor[i] != bbc)
	    bb = 99;
	}
	bb++;
	bbc = sqcolor[i];
	break;

      case (wknight):
	score += scentral[i];
	score += s_knight_mobility(i);
	wn++;
	break;

      case (bknight):
	score -= scentral[i];
	score -= s_knight_mobility(i);
	bn++;
	break;

      case (wqueen):
	score += scentral[i];
	score += s_rook_mobility(i);
	score += s_bishop_mobility(i);
	break;

      case (bqueen):
	score -= scentral[i];
	score -= s_rook_mobility(i);
	score -= s_bishop_mobility(i);
	break;

      case (wking):
	score += scentral[i] >> 1;
	score += s_king_mobility(i);
	wk++;
	break;

      case (bking):
	score -= scentral[i] >> 1;
	score -= s_king_mobility(i);
	bk++;
	break;
    }
  }

  /* opposite color bishops */
  if ((wb < 99) && (bb < 99) && (wbc != bbc) && (piece_count < 32))
    {
	score = (int)((float)score * (float)((float)piece_count / 32.0));
    }
  
  storeECache(score);
  
  /* adjust for color: */
  if (white_to_move == 1) {
    return score;
  }
  else {
    return -score;
  }

}