Keep track of PV

Use the triangular-array method (Fairy-Max style) to keep track of the PV.

diff --git a/hachu.c b/hachu.c
index 3ea5599..05529dc 100644 (file)
--- a/hachu.c
+++ b/hachu.c
@@ -84,9 +84,9 @@ typedef struct {
   int from, to, piece, victim, new, booty, epSquare, epVictim, ep2Square, ep2Victim, savKeyL, savKeyH;\r
 } UndoInfo;\r
 \r
-int stm, xstm, hashKeyH, hashKeyL, framePtr, msp, nonCapts, rootEval, retMSP, retFirst, level, chuFlag=1;\r
+int stm, xstm, hashKeyH, hashKeyL, framePtr, msp, nonCapts, rootEval, retMSP, retFirst, pvPtr, level, chuFlag=1;\r
 int nodes, startTime, tlim1, tlim2;\r
-Move retMove, moveStack[10000], path[100];\r
+Move retMove, moveStack[10000], path[100], pv[1000];\r
 \r
 #define X 36 /* slider              */\r
 #define J -1 /* jump                */\r
@@ -1190,6 +1190,7 @@ int
 Search (int alpha, int beta, int difEval, int depth, int oldPromo, int promoSuppress)\r
 {\r
   int i, j, k, firstMove, oldMSP = msp, curMove, sorted, bad, phase, king, iterDep, replyDep, nextVictim, to, defer, dubious, bestMoveNr;\r
+  int myPV = pvPtr;\r
   int score, bestScore, curEval, iterAlpha;\r
   Move move, nullMove;\r
   UndoInfo tb;\r
@@ -1212,6 +1213,9 @@ if(PATH) printf("search(%d) %d-%d eval=%d, stm=%d\n",depth,alpha,beta,difEval,st
   alpha -= (alpha < curEval);\r
   beta  -= (beta <= curEval);\r
 \r
+  nodes++;\r
+  pv[pvPtr++] = 0; // start empty PV, directly behind PV of parent\r
+\r
   firstMove = curMove = sorted = msp += 20; // leave 20 empty slots in front of move list\r
   phase = 0; iterDep=1; replyDep = (depth < 1 ? depth : 1) - 1;\r
   do {\r
@@ -1347,6 +1351,10 @@ if(PATH) printf("%d:%2d:%d %3d %6x %-10s %6d %6d\n", level, depth, iterDep, curM
            // update killer\r
            goto cutoff;\r
          }\r
+         { int i=pvPtr;\r
+           for(pvPtr = myPV+1; pv[pvPtr++] = pv[i++]; ); // copy daughter PV\r
+           pv[myPV] = move;                              // behind our move (pvPtr left at end of copy)\r
+         }\r
        }\r
 \r
       }\r
@@ -1360,7 +1368,8 @@ if(PATH) printf("%d:%2d:%d %3d %6x %-10s %6d %6d\n", level, depth, iterDep, curM
   } while(++iterDep <= depth); // next depth\r
   retMSP = msp;\r
   retFirst = firstMove;\r
-  msp = oldMSP;\r
+  msp = oldMSP; // pop move list\r
+  pvPtr = myPV; // pop PV\r
   retMove = bestMoveNr ? moveStack[bestMoveNr] : 0;\r
 if(flag && depth >= 0) printf("return %d: %d %d\n", depth, bestScore, curEval);\r
   return bestScore + (bestScore < curEval);\r