transpositiontable.cpp

EVC4.0开发的国际象棋的元代码

/****************************************************
Author: S. Senthil kumar
File: TranspositionTable.cpp
Purpose:    Implementation of the board transposition table

******************************************************/


#include "Global.h"
#include "OneMove.h"
#include "TransTableEntry.h"
#include "TranspositionTable.h"



TransTableEntry::TransTableEntry()
	{
		valid=0;
	}




TranspositionTable::TranspositionTable()
	{
		//Initialize TranspositionTable
		srand(32727);
		for (int i=0;i<7;i++)
		{
			for (int j=0;j<8;j++)
			{
				for (int k=0;k<8;k++)
				{
					
					ZobristTable[i][j][k]=abs(rand());
					HashLockTable[i][j][k]=abs(rand());
				}
			}
		}
		//Invalidate all entries initially.
		for (int x=0;x<HASH_SIZE;x++)
		{
			hashtable[x].valid=0;
		}
		tdebug=0;

	}
		
		
	
void TranspositionTable::AddEntry(int board[8][8],TransTableEntry entry)
	{
		
		int hashcode=GetHashCode(board) % HASH_SIZE;
		int hashlock=GetHashLock(board);

		TransTableEntry e=hashtable[hashcode];	
		if (e.valid)
		{
			//If new entry has greater or equal depth, replace entry with new one.
			if ((e.depth==entry.depth && e.value<entry.value) || (e.depth<entry.depth))
			{
				
				e.move=entry.move;
				e.depth=entry.depth;
				e.value=entry.value;
				e.hashlock=hashlock;
				hashtable[hashcode]=e;
			}
		}
		else
		{
			//No entry for current board posn. Set parameters for the new entry and add to hashtable
			e.valid=1;
			e.move=entry.move;
			e.depth=entry.depth;
			e.value=entry.value;
			e.next=NULL;
			e.hashlock=hashlock;
			e.valid=1;
			hashtable[hashcode]=e;
			
		}	
		tdebug=0;
	}
	TransTableEntry TranspositionTable::LookUp(int board[8][8])
	{
		
		//Checks to see if entry present. Otherwise returns dummy invalid entry.	
		int hashcode=GetHashCode(board) % HASH_SIZE;
		TransTableEntry dummy;dummy.valid=0;
		
		TransTableEntry e=hashtable[hashcode];	
		if (hashcode<0 || e.valid==0) return dummy;
		
		
		if (e.hashlock==GetHashLock(board))
		{
			return e;
		}
		else
		{
			return dummy;
		}

	}
	//Not necessary. For debugging purposes
	CString TranspositionTable::GetBoardArray(int board[8][8])
	{
		
		CString boardarray;
		char buf[10];
		for (int i=0;i<8;i++)
		{
			for (int j=0;j<8;j++)
			{
				if (board[i][j]<10)
					boardarray+="W"+(CString)itoa(board[i][j],buf,10);
				else
					boardarray+=itoa(board[i][j],buf,10);
			}
				
		
		}
		return boardarray;
	}
		
	
	
	int TranspositionTable::GetHashCode(int board[8][8])
	{
	
		//Generates hash code
		int key=0;
		//Iterate through each board position
		//Xor repeatedly by indexing with piece,xposn,yposn on ZobristTable(random no table)
		for (int i=0;i<8;i++)
		{
			for (int j=0;j<8;j++)
			{
				if (board[i][j]!=0)
				{
						
						key=key^ZobristTable[board[i][j]%10][i][j];
						
					}			
				
				}
			
		}
		return key;
		
	}

	int TranspositionTable::GetHashLock(int board[8][8])
	{
	
		//Hashlock for double protection against duplicate Zobrist Keys
		//Same procedure as ZobristKey
		int hashlock=0;
		for (int i=0;i<8;i++)
		{
			for (int j=0;j<8;j++)
			{
					if (board[i][j]!=0)
					{
						
						hashlock=hashlock^HashLockTable[board[i][j]%10][i][j];
					
					}			
				
				}
			
		}
		return hashlock;
	}