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broken?
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Folkert van Heusden



Joined: 14 Mar 2008
Posts: 67
Location: Gouda, the Netherlands
PostPost subject: broken?    Posted: Sun Jul 08, 2012 5:01 pm Reply to topic Reply with quote
Hi,

As you people might have noticed, I've been working on my chess engine.
It'll become the original POS in a deep (multithreaded) brute force way.
First step is implementing a brute-force thingy, then bolting on the evaluator of the original pos. That last step won't be too difficult, but this brute force alpha/beta code; something is wrong with it.
I googled a little and it seems all implementations are different. Not just naming of variables and such, but how they work too. For example the implementation on wikipedia (english) seems to totally wrong.
So maybe you people could take a look at my code and tell me what is wrong?

Code:
int alphaBeta(final Scene scene, final PlayerColor side, final PlayerColor rootSide, final double finishBefore, int depth, final int maxExtension, final IO io, int alpha, int beta) throws IOException {
   // keep track of the number of processed nodes
   nodeCount.addAndGet(1);

   final PlayerColor otherSide = Statics.opponentColor(side);
   if (depth <= 0) {
      // if the bottom of the tree is check, search a little deeper
      if (depth > maxExtension && scene.isKingUnderAttack(side, otherSide) && !scene.isCheckMate(side)) {
         // if check then extend the searchdepth
         // by entering this if, the 'depth--' is not invoked and also the next 'depth == 0' is not triggered
         //io.progressCallback("Search depth extension due to check " + depth);
         long now = System.currentTimeMillis();
         if (now - prev.get() > 5000) { // emit output after 5s
            double took = Statics.getTimestamp() - startTs;
            io.progressCallbackDepthReached(maxDepth - depth);
            prev.set(now);
         }
      }
      else {
         return getShannonValue(scene, side); // score
      }
   }
   depth--;

   final List<Move> moves = scene.getMoveList(side);
   int movesListSize = moves.size();
   totalNMoves.addAndGet(movesListSize);
   totalNodes.addAndGet(1);
   for(int index=0; index<movesListSize; index++) {

      // "do a move", 'afterMove' is the "situation" after 'currentMove' was executed
      Scene afterMove = null;
      final Move currentMove = moves.get(index);
      try {
         afterMove = currentMove.getScene();
         if (afterMove == null)
            afterMove = scene.Move(currentMove);
         else
            currentMove.setScene(null); // help GC, link is not required
         afterMove.validateMoves(otherSide);
      }
      catch(Exception e) {
         System.out.println(" side: " + side + " alpha " + alpha + " beta " + beta);
         System.out.println(" " + (depth + 1) + " " + currentMove);
         Statics.displayBoard(afterMove.getBoard());
         System.out.println("" + e);
         e.printStackTrace();
         System.exit(1);
      }

      final int score = alphaBeta(afterMove, otherSide, rootSide, finishBefore, depth, maxExtension, io, alpha, beta);
      if (score == -Integer.MAX_VALUE || score == Integer.MAX_VALUE)
         continue;
      afterMove.shrink();

      if (side == rootSide) { // MAX
         if (score >= beta)
            return beta;
         if (score > alpha)
            alpha = score;
      }
      else { // opposite side: MIN
         if (score <= alpha)
            return alpha;
         if (score < beta)
            beta = score;
      }

      double nowTs = Statics.getTimestamp();
      if (finishBefore > 0 && finishBefore <= nowTs) {
         io.progressCallback("Abort search due to time limit");
         break;
      }
   }

   if (side == rootSide)
      return alpha;
   
   return beta;
}

_________________
http://www.vanheusden.com/pos/ - takes 'experimental' to a whole new level
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Display posts from previous:   
Subject Author Date/Time
broken? Folkert van Heusden Sun Jul 08, 2012 5:01 pm
      Re: broken? Tim Kosse Sun Jul 08, 2012 5:43 pm
            Re: broken? Folkert van Heusden Sun Jul 08, 2012 6:13 pm
      Re: broken? Zong Li Sun Jul 08, 2012 5:47 pm
            Re: broken? Folkert van Heusden Sun Jul 08, 2012 6:15 pm
                  Re: broken? Zong Li Sun Jul 08, 2012 6:37 pm
                        Re: broken? Folkert van Heusden Sun Jul 08, 2012 6:53 pm
                              Re: broken? Tim Kosse Sun Jul 08, 2012 7:04 pm
                                    Re: broken? Folkert van Heusden Sun Jul 08, 2012 7:35 pm
                                          Re: broken? Sven Schüle Sun Jul 08, 2012 9:15 pm
                                                Re: broken? Balint Pfliegel Sun Jul 08, 2012 9:56 pm
                                                      Re: broken? Zong Li Sun Jul 08, 2012 11:31 pm
                                                Re: broken? Sven Schüle Sun Jul 08, 2012 11:25 pm
                              Re: broken? Zong Li Sun Jul 08, 2012 7:35 pm
      Re: broken? Sven Schüle Sun Jul 08, 2012 6:01 pm
            Re: broken? Folkert van Heusden Sun Jul 08, 2012 6:25 pm
      Re: broken? Aart Bik Sun Jul 08, 2012 10:22 pm
            Re: broken? Balint Pfliegel Sun Jul 08, 2012 10:40 pm
                  Re: broken? Adam Hair Mon Jul 09, 2012 12:22 am
                  Re: broken? Aart Bik Mon Jul 09, 2012 12:37 am
                        Re: broken? Aart Bik Mon Jul 09, 2012 12:57 am
                        Re: broken? Balint Pfliegel Mon Jul 09, 2012 5:47 am
      Re: broken? Aart Bik Mon Jul 09, 2012 4:45 pm
            Re: broken? Folkert van Heusden Mon Jul 09, 2012 6:35 pm
                  Re: broken? Zong Li Mon Jul 09, 2012 6:49 pm
                        Re: broken? Folkert van Heusden Mon Jul 09, 2012 7:17 pm
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