Beispiel #1
0
        private MCTSAZNode Select(MCTSAZNode root)
        {
            while (root.Children.Count != 0)             //Look for a leaf node (one we haven't expanded yet)
            {
                MCTSAZNode bestNext  = null;
                double     bestValue = double.MinValue;

                for (var i = 0; i < root.Children.Count; i++)
                {
                    var    c        = root.Children[i];
                    double uctValue = c.AverageValue + c.CalculateUCT(_random, root, root.NetworkResult.MoveRating[c.NetworkChildIndex]);
                    // small random number to break ties randomly in unexpanded nodes
                    if (root.Parent == null)
                    {
                        uctValue *= _random.NextDouble();
                    }

                    if (uctValue > bestValue)
                    {
                        bestNext  = c;
                        bestValue = uctValue;
                    }
                }

                root = bestNext;
            }

            return(root);
        }
Beispiel #2
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        public double CalculateUCT(Random random, MCTSAZNode parent, float priorProbability)
        {
            //https://web.stanford.edu/~surag/posts/alphazero.html
            //Page 8 https://www.nature.com/articles/nature24270.epdf?author_access_token=VJXbVjaSHxFoctQQ4p2k4tRgN0jAjWel9jnR3ZoTv0PVW4gB86EEpGqTRDtpIz-2rmo8-KG06gqVobU5NSCFeHILHcVFUeMsbvwS-lxjqQGg98faovwjxeTUgZAUMnRQ

            return(ExplorationParameter * (priorProbability + Epsilon) * Math.Sqrt(parent.VisitCount + 1) / (1 + VisitCount));
        }
Beispiel #3
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        public void Reset()
        {
            Children.Clear();
            Value         = 0;
            VisitCount    = 0;
            AverageValue  = 0;
            Parent        = null;
            NetworkResult = null;

            PieceToPurchase   = null;
            NetworkChildIndex = -1;
        }
Beispiel #4
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        /// <summary>
        /// Finds the best child based on their VisitCount
        /// </summary>
        /// <returns></returns>
        internal MCTSAZNode FindBestChild(MCTSAZNode root)
        {
            //Perform the best move
            var best           = root.Children[0];
            int bestVisitCount = root.Children[0].VisitCount;

            for (var index = 1; index < root.Children.Count; index++)
            {
                var child = root.Children[index];
                if (child.VisitCount > bestVisitCount)                 //TODO: Handle draws
                {
                    best           = child;
                    bestVisitCount = child.VisitCount;
                }
            }

            return(best);
        }
Beispiel #5
0
 private void Expand(MCTSAZNode root)
 {
     root.Expand(_client);
 }