Implement abort of search on long thinking time

A global variable abortFlag is tested to make the search unwind. A function
TerminalCheck() is added to read the clock and set this variable if needed,
based on the tlim3 time limit. Measures have been taken to make sure the
root node returns a valid move and score even when interrupted during the
search of the first move.

diff --git a/hachu.c b/hachu.c
index a926e65..478a20b 100644 (file)
--- a/hachu.c
+++ b/hachu.c
@@ -114,7 +114,8 @@ typedef struct {
 char *array, fenArray[4000], *reason;\r
 int bWidth, bHeight, bsize, zone, currentVariant, chuFlag, tenFlag, chessFlag, repDraws;\r
 int stm, xstm, hashKeyH, hashKeyL, framePtr, msp, nonCapts, rootEval, retMSP, retFirst, retDep, pvPtr, level, cnt50, mobilityScore;\r
-int nodes, startTime, tlim1, tlim2, repCnt, comp;\r
+int nodes, startTime, tlim1, tlim2, tlim3, repCnt, comp, abortFlag;\r
+Move ponderMove;\r
 Move retMove, moveStack[10000], path[100], repStack[300], pv[1000], repeatMove[300], killer[100][2];\r
 \r
       int maxDepth;                            // used by search\r
@@ -1565,6 +1566,8 @@ FireSet (UndoInfo *tb)
     if(p[i].pos != ABSENT) tb->fireMask |= fireFlags[i-2];\r
 }\r
 \r
+void TerminationCheck();\r
+\r
 #define QSdepth 0\r
 \r
 int\r
@@ -1573,7 +1576,7 @@ Search (int alpha, int beta, int difEval, int depth, int oldPromo, int promoSupp
   int i, j, k, firstMove, oldMSP = msp, curMove, sorted, bad, phase, king, iterDep, replyDep, nextVictim, to, defer, dubious, bestMoveNr;\r
   int resDep;\r
   int myPV = pvPtr;\r
-  int score, bestScore, curEval, iterAlpha;\r
+  int score, bestScore, oldBest, curEval, iterAlpha;\r
   Move move, nullMove;\r
   UndoInfo tb;\r
 #ifdef HASH\r
@@ -1598,7 +1601,7 @@ if(PATH) /*pboard(board),pmap(attacks, BLACK),*/printf("search(%d) {%d,%d} eval=
   alpha -= (alpha < curEval);\r
   beta  -= (beta <= curEval);\r
 \r
-  nodes++;\r
+  if(!(nodes++ & 4095)) TerminationCheck();\r
   pv[pvPtr++] = 0; // start empty PV, directly behind PV of parent\r
 \r
 \r
@@ -1779,6 +1782,11 @@ level--;
     repetition:\r
       UnMake(&tb);\r
       xstm = stm; stm ^= WHITE;\r
+      if(abortFlag > 0) { // unwind search\r
+printf("# abort (%d) @ %d\n", abortFlag, level);\r
+        if(curMove == firstMove) bestScore = oldBest, bestMoveNr = firstMove; // none searched yet\r
+        goto leave;\r
+      }\r
 #if 1\r
 if(PATH) printf("%d:%2d:%d %3d %6x %-10s %6d %6d\n", level, depth, iterDep, curMove, moveStack[curMove], MoveToText(moveStack[curMove], 0), score, bestScore);\r
 \r
@@ -1842,6 +1850,7 @@ if(PATH) printf("%d:%2d:%d %3d %6x %-10s %6d %6d\n", level, depth, iterDep, curM
     } else hashTable[index].move[hit] = 0;\r
 #endif\r
   } // next depth\r
+leave:\r
   retMSP = msp;\r
   retFirst = firstMove;\r
   msp = oldMSP; // pop move list\r
@@ -2088,7 +2097,7 @@ ListMoves ()
   int i;\r
   for(i=0; i< BSIZE; i++) boardCopy[i] = !!board[i];\r
 MapFromScratch(attacks);\r
-  postThinking--; repCnt = 0; tlim1 = tlim2 = 1e8; msp = 0;\r
+  postThinking--; repCnt = 0; tlim1 = tlim2 = tlim3 = 1e8; abortFlag = msp = 0;\r
   Search(-INF-1, INF+1, 0, 1, sup1 & ~PROMOTE, sup2);\r
   postThinking++;\r
   listStart = retFirst; listEnd = msp = retMSP;\r
@@ -2214,6 +2223,7 @@ SetSearchTimes (int timeLeft)
   if(timePerMove > 0) targetTime = 0.5*timeLeft, movesLeft = 1;\r
   tlim1 = 0.2*targetTime;\r
   tlim2 = 1.9*targetTime;\r
+  tlim3 = 5*timeLeft / (movesLeft + 4.1);\r
 }\r
 \r
 int\r
@@ -2274,6 +2284,12 @@ printf("# setup done");fflush(stdout);
       }\r
     }\r
 \r
+    void\r
+    TerminationCheck()\r
+    {\r
+        if(GetTickCount() - startTime > tlim3) abortFlag = 2;\r
+    }\r
+\r
     main()\r
     {\r
       int engineSide=NONE;                     // side played by engine\r
@@ -2288,6 +2304,7 @@ printf("# setup done");fflush(stdout);
 \r
         if(listEnd == 0) ListMoves();   // always maintain a list of legal moves in root position\r
 \r
+        abortFlag = 0;\r
         if(stm == engineSide) {         // if it is the engine's turn to move, set it thinking, and let it move\r
      \r
 pboard(board);\r