From 6a1bd09c5d3c876e4dfa565438a5d3d549fdd2f1 Mon Sep 17 00:00:00 2001
From: H.G. Muller <h.g.muller@hccnet.nl>
Date: Mon, 11 Feb 2013 22:12:49 +0100
Subject: [PATCH] Keep track of piece pairs, with configurable bonus

A new array bp[] is added, indexed by piece type, to store the pair
bonuses for each piece type. The bonus is awarded on capture when the
piece count kept in pl[] for that type becomes odd.
 The value can be specified as the 'move rights' of a step vector 0,
appended to the piece description.
---
 fairymax.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/fairymax.c b/fairymax.c
index 6ae3170..9782ba4 100644
--- a/fairymax.c
+++ b/fairymax.c
@@ -130,7 +130,7 @@ oo[32],                                        /* initial piece setup      */
 of[256],
 od[16];                                        /* 1st dir. in o[] per piece*/
 
-signed char L,pl[32],
+signed char L,pl[32],pb[32],
 b[513],                                        /* board: 16x8+dummy, + PST */
 T[4104],                                       /* hash translation table   */
 centr[32],
@@ -201,7 +201,7 @@ int k,q,l,e,E,z,n;      /* (q,l)=window, e=current eval. score, E=e.p. sqr.*/
         v+=centr[p]?b[x+257]-b[y+257]:0;       /* center positional pts.   */
         if(!(G&S))b[FF]=b[G],v+=50;            /* castling: put R & score  */
         b[G]=b[H]=0;b[x]=gt;b[y]=u|32;         /* do move, set non-virgin  */
-        pl[t&31]-=!!t;                         /* updat victim piece count */
+        i+=-((pl[t&31]-=!!t)&1)&pb[t&31];/* update piece count, pair bonus */
         v-=w[p]>0|R<EG?0:20;                   /*** freeze K in mid-game ***/
         if(p<3)                                /* pawns:                   */
         {v-=9*((x-2&M||b[x-2]-u)+              /* structure, undefended    */
@@ -404,6 +404,7 @@ void InitGame()
  for(i=0; i<BW; i++) {
   R += abs(w[oo[i]])/FAC + abs(w[oo[i+16]])/FAC;
   Q += abs(w[oo[i]]) - abs(w[oo[i+16]]) + w[1] - w[2];
+  Q += (pl[i]>>1)*pb[i] -(pl[i+16]>>1)*pb[i];
   if(w[oo[i]] < 0) k = w[oo[i]];
  }
  R -= 2*(-k/FAC);
@@ -512,6 +513,8 @@ void LoadGame(char *name)
               blacktype[c&31]=i; piecename[i]=c&31;
               if(piecetype[c&31]==0) piecetype[c&31]=i; // only first
               succession |= w[i] < -4;         // expendable royalty; assume we can promote to it
+            } else {
+              if(!o[j]) pb[i] = pb[i+16] = of[j--]; // hand-set pair bonus
             }
             j++; o[j]=0;
             /* printf("# c='%c' i=%d od[i]=%d j=%d (%3d,%8x)\n",c?c:' ',i,od[i],j,o[j-1],of[j-1]); /**/
@@ -857,7 +860,7 @@ int main(int argc, char **argv)
 					case 0: // undefined piece, ignore
                                             break;
                                         }
-                                        pl[BLACK+WHITE-color]++;pl[p+color]++;
+                                        pl[BLACK+WHITE-color]++; if(pl[p+color]++&1) Q+=pb[p];
                                         if(w[p+color] == -1)pl[p+color]=1; // fake we have one if value = -1, to thwart extinction condition
                                         continue;
                                     }
-- 
1.7.0.4