killer.cpp

/*
	Copyright (C) 2015 Matthew Lai

	Giraffe is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.
	
	Giraffe is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.
	
	You should have received a copy of the GNU General Public License
	along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "killer.h"

#include <limits>
#include <algorithm>

Killer::Killer()
{
}

void Killer::Notify(int32_t ply, Move move)
{
	if (m_killerMoves.size() < (static_cast<size_t>(ply) + 1))
	{
		m_killerMoves.resize(ply + 1);

		for (size_t i = 0; i < NUM_KILLER_MOVES_PER_PLY; ++i)
		{
			m_killerMoves[ply].moves[i] = 0;
			m_killerMoves[ply].moves[i] = 0;
		}
	}

	// if the move is already in the table, we don't need to do anything
	if (m_killerMoves[ply].moves[0] == move)
	{
		return;
	}

	// otherwise, push everything down one slot
	for (int64_t i = (NUM_KILLER_MOVES_PER_PLY - 1); i >= 0; --i)
	{
		if (i == 0)
		{
			m_killerMoves[ply].moves[i] = move;
		}
		else
		{
			m_killerMoves[ply].moves[i] = m_killerMoves[ply].moves[i - 1];
		}
	}
}

void Killer::GetKillers(KillerMoveList &moveList, int32_t ply)
{
	moveList.Clear();

	if (m_killerMoves.size() < (static_cast<size_t>(ply) + 1))
	{
		return;
	}

	// moves from the current ply
	for (size_t i = 0; i < NUM_KILLER_MOVES_PER_PLY; ++i)
	{
		moveList.PushBack(m_killerMoves[ply].moves[i]);
	}

	// moves from the ply-2
	if (ply >= 2)
	{
		for (size_t i = 0; i < NUM_KILLER_MOVES_PER_PLY; ++i)
		{
			moveList.PushBack(m_killerMoves[ply - 2].moves[i]);
		}
	}

	// moves from the ply+2
	if ((static_cast<size_t>(ply) + 2) < m_killerMoves.size())
	{
		for (size_t i = 0; i < NUM_KILLER_MOVES_PER_PLY; ++i)
		{
			moveList.PushBack(m_killerMoves[ply + 2].moves[i]);
		}
	}
}

void Killer::MoveMade()
{
	// if a move is made, we decrement all plies

	for (size_t ply = 1; ply < m_killerMoves.size(); ++ply)
	{
		m_killerMoves[ply - 1] = m_killerMoves[ply];
	}
}