logic: Added monteCarlo.py as an incomplete implementation of MCTS.

1 files changed, 59 insertions, 0 deletions

diff --git a/imago/engine/monteCarlo.py b/imago/engine/monteCarlo.py
new file mode 100644
index 0000000..13f5c47
--- /dev/null
+++ b/imago/engine/monteCarlo.py
@@ -0,0 +1,59 @@
+"""Monte Carlo Tree Search module."""
+
+class MCTS:
+    """Monte Carlo tree."""
+
+    def __init__(self, root):
+        self.root = root
+
+    def selection(self):
+        """Select the most promising node with unexplored children."""
+        bestUCB = 0
+        bestNode = None
+        bestUCB, bestNode = self._selectionRec(self.root, bestUCB, bestNode)
+        return bestNode
+
+    def __selectionRec(self, node, bestUCB, bestNode):
+
+        # Check if node has unexplored children and better UCB than previously explored
+        if len(node.unexploredVertices) > 0:
+            ucb = node.ucb()
+            if ucb > bestUCB:
+                bestUCB = ucb
+                bestNode = node
+
+        # Recursively search children for better UCB
+        for child in node.children:
+            bestUCB, bestNode = self._selectionRec(child, bestUCB, bestNode)
+
+        return bestUCB, bestNode
+
+    def expansion(self, node):
+        # Get a random unexplored vertex and remove it from the set
+        newVertex = node.unexploredVertices.pop()
+        newNode = MCTSNode(newVertex[0], newVertex[1], node)
+        parent.children.add(self)
+        return newNode
+
+    def simulation(self, node):
+
+    def backup(self, node):
+
+
+class MCTSNode:
+    """Monte Carlo tree node."""
+
+    def __init__(self, move, parent):
+        self.visits = 0
+        self.score = 0
+        self.move = move
+        self.parent = parent
+        self.children = set()
+        self.unexploredVertices = move.getPlayableVertices()
+
+    def ucb(self):
+        """Returns Upper Confidence Bound of node"""
+        # meanVictories + 1/visits
+        mean = self.score / self.visits
+        adjust = 1/self.visits
+        return mean + adjust