leval.c   [plain text]

```/*
Sjeng - a chess variants playing program

This program is free software; you can redistribute it and/or modify
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: leval.c
Purpose: functions for evaluating positions in losers chess

*/

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

static int lcentral[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,-15,-15,-15,-15,-15,-15,-20,0,0,
0,0,-15,0,3,5,5,3,0,-15,0,0,
0,0,-15,0,15,15,15,15,0,-15,0,0,
0,0,-15,0,15,30,30,15,0,-15,0,0,
0,0,-15,0,15,30,30,15,0,-15,0,0,
0,0,-15,0,15,15,15,15,0,-15,0,0,
0,0,-15,0,3,5,5,3,0,-15,0,0,
0,0,-20,-15,-15,-15,-15,-15,-15,-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 int l_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;
}

static int l_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;
}

static int l_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;
}

static int l_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;
}

static int l_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;
}

int32_t losers_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;
int i, a, j;
int32_t score = 0;
int in_cache;
int wp = 0, bp = 0;
int wks, bks;
int wpassp = 0, bpassp = 0;
int wpawns = 0, bpawns = 0;

in_cache = 0;

checkECache(&score, &in_cache);

if(in_cache)
{
if (white_to_move == 1) return score;
return -score;
}

/* 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++;

switch (board[i]) {
case (wpawn):
wp++;
wpawns++;
score += lcentral[i];
score += l_pawn_mobility(i) << 2;
score += (rank(i) - 2) * 8;
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 -= 8*(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 += 25 + 10*(rank(i)-2);

if (rank(i) == 7) score += 50;

wpassp++;

/* 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 += 24;
}
}

/* check for pawn islands */
if (!pawns[1][pawn_file-1])
score -= 5;

break;

case (bpawn):
bp++;
bpawns++;
score -= lcentral[i];
score -= l_pawn_mobility(i) << 2;
score -= (7 - rank(i)) * 8;
isolated = FALSE;
backwards = FALSE;

/* 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 += 8*(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 -= 25 + 10*(7-rank(i));

if (rank(i) == 2) score -= 50;

bpassp++;

/* 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 -= 24;
}
}

if (!pawns[0][pawn_file-1])
score += 5;

break;

case (wrook):
wp++;
score += l_rook_mobility(i) << 2;
score += lcentral[i];
break;

case (brook):
bp++;
score -= l_rook_mobility(i) << 2;
score -= lcentral[i];
break;

case (wbishop):
wp++;
score += l_bishop_mobility(i) << 2;
score += lcentral[i];
break;

case (bbishop):
bp++;
score -= l_bishop_mobility(i) << 2;
score -= lcentral[i];
break;

case (wknight):
wp++;
score += lcentral[i] << 1;
score += l_knight_mobility(i) << 2;
break;

case (bknight):
bp++;
score -= lcentral[i] << 1;
score -= l_knight_mobility(i) << 2;
break;

case (wqueen):
wp++;
score += l_bishop_mobility(i) << 1;
score += l_rook_mobility(i) << 1;
score += lcentral[i];
break;

case (bqueen):
bp++;
score -= l_bishop_mobility(i) << 1;
score -= l_rook_mobility(i) << 1;
score -= lcentral[i];
break;

case (wking):
/* being in center is BAD */
wks = lcentral[i] << 1;
score += l_king_mobility(i);
break;

case (bking):
/* being in center is BAD */
bks = lcentral[i] << 1;
score -= l_king_mobility(i);
break;
}
}

if (wp + bp > 10)
{
score -= wks - bks;
}

if (abs(Material) <= 900)
{
score += Material;
}
else
{
/* one side has a huge advantage, which could
* become problematic */
/* only apply this to self, we assume somebody
* else can handle this just fine */

/* I would swear the colors are reversed here,
* but it works this way and not otherwise :) */

/* disable this if we have passers...else they'll
just sit on last rank */

if (Material > 0 && comp_color == !WHITE && !wpassp)
{
score += 1800 - Material;
}
else if (Material < 0 && comp_color == !BLACK && !bpassp)
{
score += -(1800 + Material);
}
else
{
score += Material;
}
}

if (!wpawns) score += 200;
else if (!bpawns) score -= 200;

if (!wp) score = INF;
else if (!bp) score = -INF;

storeECache(score);