Implement history heuristic

The non-captures are now sorted by history score before searching them.

diff --git a/dropper.c b/dropper.c
index 0b19726..5acff77 100644 (file)
--- a/dropper.c
+++ b/dropper.c
@@ -71,6 +71,7 @@ int handVal[96], rawGain[97];
 unsigned int moveStack[500*MAXPLY];
 int killers[MAXPLY][2];
 int path[MAXPLY], deprec[MAXPLY];
+int history[1<<16];
 unsigned char checkHist[MAXMOVES+MAXPLY];
 int repKey[512+20];
 
@@ -1077,6 +1078,12 @@ UnMake (StackFrame *f)
 //ply==0 || path[0]==0x0017b1 && (ply==1 || (ply==2))
 
 int
+HisComp (const void *x, const void*y)
+{
+    return history[*(int *)y & 0xFFFF] - history[*(int *)x & 0xFFFF];
+}
+ 
+int
 Search (int stm, int alpha, int beta, StackFrame *ff, int depth, int reduction, int maxDepth)
 {
     MoveStack m; StackFrame f; HashEntry *entry;
@@ -1213,6 +1220,7 @@ if(PATH)printf("%d:%d:%d new iter moveStack[%d..%d]\n",ply,depth,iterDepth,m.fir
                        if(PseudoLegal(stm, killer2)) moveStack[moveSP++] = moveStack[m.late], moveStack[m.late++] = killer2; // (original goes to end)
                        m.drops = moveSP;
                        // here we can sort based on history
+                       if(moveSP > m.late) qsort(moveStack + m.late, moveSP - m.late, sizeof(int), &HisComp);
                        m.stage = 1; if(moveSP > curMove) break;
                      case 1:
                        if(f.checker != CK_NONE) {
@@ -1282,6 +1290,7 @@ printf("%d:%d:%d %2d. %08x %c%d%c%d %6d %6d %6d\n",ply,depth,iterDepth,curMove,m
                if(score > alpha) {
                    int *tail;
                    alpha = score;
+                   history[moveStack[curMove] & 0xFFFF] += iterDepth*iterDepth;
                    if(score >= beta) { // beta cutoff
                        if(curMove >= m.nonCapts && moveStack[curMove] != killers[ply][1])
                            killers[ply][0] = killers[ply][1], killers[ply][1] = moveStack[curMove];
@@ -1684,7 +1693,7 @@ printf("# command: %s\n", inBuf);
 int
 main ()
 {
-  int score;
+  int score, i;
 
   EngineInit(); SetMemorySize(1);  // reserve minimal hash to prevent crash if GUI sends no 'memory' command
   GameInit("zh"); Setup(startPos); // to facilitate debugging from command line
@@ -1696,6 +1705,7 @@ main ()
     if(stm == engineSide) {         // if it is the engine's turn to move, set it thinking, and let it move
 
       nodeCount = forceMove = undoInfo.move = abortFlag = 0; ReadClock(1);
+      for(i=0;i<1<<16;i++) history[i] = 0; //>>= 1;
       score = Search(stm^COLOR, -INF, INF, &undoInfo, maxDepth, 0, maxDepth);
 
       if(!undoInfo.move) {             // no move, game apparently ended