uct.h

// Copyright (c) 2012, Jacob Burnim <jburnim@gmail.com>
// All rights reserved.

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//  - Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
//  - Redistributions in binary form must reproduce the above
//    copyright notice, this list of conditions and the following
//    disclaimer in the documentation and/or other materials provided
//    with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
// OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef UCT_H_
#define UCT_H_

#define DEBUG_SCORE

#include "game.h"

const double UCT_FACTOR = 3.0;
const double EPSILON = 1e-6;

struct node_t {
  // How many times has this node been visited?
  int n_visits;

  // What sum of scores have we achieved across all visits?
  int total_score;

  // Pointer to first/leftmost child.
  node_t* child;

  // Pointer to next sibling.
  node_t* next;

  // What move brought us to this position?
  move_t move;

#ifdef DEBUG_SCORE
  int total_scores[4];
#endif  // DEBUG_UTILITY
};

void uct_move(const int n_moves, const state_t& state, move_t* move);

#endif  // UCT_H_