Example #1
0
 /** Returns the best move to make from here during a playout. */
 short bestSearchMove(SearchNode node, McRunnable runnable) {
   final Board runnableBoard = runnable.getBoard();
   final MersenneTwisterFast random = runnable.getRandom();
   short result = node.getWinningMove();
   if (result != NO_POINT && runnableBoard.isLegal(result)) {
     // The isLegal() check is necessary to avoid superko violations
     return result;
   }
   float bestSearchValue = searchValue(node, PASS);
   result = PASS;
   final ShortSet vacantPoints = runnableBoard.getVacantPoints();
   int start;
   start = random.nextInt(vacantPoints.size());
   int i = start;
   final int skip = PRIMES[random.nextInt(PRIMES.length)];
   do {
     final short move = vacantPoints.get(i);
     final float searchValue = searchValue(node, move);
     if (searchValue > bestSearchValue) {
       if (runnable.isFeasible(move) && runnableBoard.isLegal(move)) {
         bestSearchValue = searchValue;
         result = move;
       } else {
         node.exclude(move);
       }
     }
     // Advancing by a random prime skips through the array
     // in a manner analogous to double hashing.
     i = (i + skip) % vacantPoints.size();
   } while (i != start);
   return result;
 }
Example #2
0
 @Override
 public short bestPlayMove() {
   double mostWins = 1;
   short result = PASS;
   final ShortSet vacantPoints = board.getVacantPoints();
   final SearchNode root = getRoot();
   do {
     mostWins = root.getWins(PASS);
     // If the move chosen on the previous pass through this loop was
     // illegal (e.g., because it was never actually tried in a playout),
     // throw it out
     if (result != PASS) {
       log("Rejected " + board.getCoordinateSystem().toString(result) + " as illegal");
       root.exclude(result);
       result = PASS;
     }
     for (int i = 0; i < vacantPoints.size(); i++) {
       final short move = vacantPoints.get(i);
       if (root.getWins(move) > mostWins) {
         mostWins = root.getWins(move);
         result = move;
       }
     }
   } while (result != PASS && !board.isLegal(result));
   // Consider resigning
   if (root.getWinRate(result) < RESIGN_PARAMETER) {
     return RESIGN;
   }
   log(
       "Selected "
           + board.getCoordinateSystem().toString(result)
           + " with "
           + root.getWins(result)
           + " wins in "
           + root.getRuns(result)
           + " runs");
   return result;
 }