Minimax Algorithm in Game Theory | Set 5 (Zobrist Hashing) (original) (raw)
`// A Java program to illustrate Zobrist Hashing Algorithm
import java.util.*;
public class GFG {
public static List<List<List>> ZobristTable = new ArrayList<>();
// mt19937 mt(01234567); public static void initialise() { for (int i = 0; i < 8; i++) { ZobristTable.add(new ArrayList<>()); for (int j = 0; j < 8; j++) { ZobristTable.get(i).add(new ArrayList<>()); for (int k = 0; k < 12; k++) { ZobristTable.get(i).get(j).add(0); } } } } // Generates a Random number from 0 to 2^64-1 public static long randomLong() { long min = 0L; long max = (long) Math.pow(2, 64); Random rnd = new Random(); return rnd.nextLong() * (max - min) + min; }
// This function associates each piece with a number public static int indexOf(char piece) { if (piece=='P') return 0; if (piece=='N') return 1; if (piece=='B') return 2; if (piece=='R') return 3; if (piece=='Q') return 4; if (piece=='K') return 5; if (piece=='p') return 6; if (piece=='n') return 7; if (piece=='b') return 8; if (piece=='r') return 9; if (piece=='q') return 10; if (piece=='k') return 11; else return -1; }
// Initializes the table public static void initTable() { for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { for (int k = 0; k < 12; k++) { Random rnd = new Random(); ZobristTable.get(i).get(j).set(k, (int) randomLong()); } } } }
// Computes the hash value of a given board public static int computeHash(List<List> board) { int h = 0; for (int i = 0; i < 8; i++) { for (int j = 0; j < 8; j++) { if (board.get(i).get(j) != '-') { int piece = indexOf(board.get(i).get(j)); h ^= ZobristTable.get(i).get(j).get(piece); } } } return h; }
public static void main(String[] args) { // Main Function // Uppercase letters are white pieces // Lowercase letters are black pieces List<List> board = new ArrayList<>(); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', 'K', '-', '-', '-', '-'))); board.add(new ArrayList<>(Arrays.asList('-', 'R', '-', '-', '-', '-', 'Q', '-'))); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', 'K', '-', '-', '-', '-'))); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', '-', '-', '-', '-', '-'))); board.add(new ArrayList<>(Arrays.asList('-', 'P', '-', '-', '-', '-', 'p', '-'))); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', '-', '-', 'p', '-', '-'))); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', '-', '-', '-', '-', '-'))); board.add(new ArrayList<>(Arrays.asList('p', '-', '-', '-', 'b', '-', '-', 'q'))); board.add(new ArrayList<>(Arrays.asList('-', '-', '-', '-', 'n', '-', '-', 'k')));
initialise();
initTable();
int hashValue = computeHash(board);
System.out.println("The hash value is : " + hashValue);
// Move the white king to the left
char piece = board.get(0).get(3);
board.get(0).set(3, '-');
hashValue ^= ZobristTable.get(0).get(3).get(indexOf(piece));
board.get(0).set(2, piece);
hashValue ^= ZobristTable.get(0).get(2).get(indexOf(piece));
System.out.println("The new hash value is : " + hashValue);
// Undo the white king move
piece = board.get(0).get(2);
board.get(0).set(2, '-');
hashValue ^= ZobristTable.get(0).get(2).get(indexOf(piece));
board.get(0).set(3, piece);
hashValue ^= ZobristTable.get(0).get(3).get(indexOf(piece));
System.out.println("The new hash value is : " + hashValue);}
}
// This code is contributed by Vaibhav
`
`using System; using System.Collections; using System.Collections.Generic; using System.Linq;
// C# program for the above approach // A program to illustrate Zobrist Hashing Algorithm // javascript code implementation
class HelloWorld {
public static List<List<List<int>>> ZobristTable = new List<List<List<int>>>();
// mt19937 mt(01234567);
public static void initialise(){
for(int i = 0; i < 8; i++){
ZobristTable.Add(new List<List<int>>());
for(int j = 0; j < 8; j++){
ZobristTable[i].Add(new List<int>());
for(int k = 0; k < 12; k++){
ZobristTable[i][j].Add(0);
}
}
}
}
// Generates a Random number from 0 to 2^64-1
public static int randomInt() {
int min = 0;
int max = (int)Math.Pow(2, 64);
Random rnd = new Random();
return rnd.Next() * (max - min) + min;
}
// This function associates each piece with
// a number
public static int indexOf(char piece)
{
if (piece=='P')
return 0;
if (piece=='N')
return 1;
if (piece=='B')
return 2;
if (piece=='R')
return 3;
if (piece=='Q')
return 4;
if (piece=='K')
return 5;
if (piece=='p')
return 6;
if (piece=='n')
return 7;
if (piece=='b')
return 8;
if (piece=='r')
return 9;
if (piece=='q')
return 10;
if (piece=='k')
return 11;
else
return -1;
}
// Initializes the table
public static void initTable()
{
for (int i = 0; i<8; i++){
for(int j = 0; j < 8; j++){
for(int k = 0; k < 12; k++){
Random rnd = new Random();
ZobristTable[i][j][k] = rnd.Next();
}
}
}
}
// Computes the hash value of a given board
public static int computeHash(List<List<char>> board)
{
int h = 0;
for (int i = 0; i<8; i++)
{
for (int j = 0; j<8; j++)
{
if (board[i][j]!='-')
{
int piece = indexOf(board[i][j]);
h ^= ZobristTable[i][j][piece];
}
}
}
return h;
}
static void Main() {
// Main Function
// Uppercase letters are white pieces
// Lowercase letters are black pieces
List<List<char>> board = new List<List<char>>();
board.Add(new List<char>(){'-', '-', '-', 'K', '-', '-', '-', '-'});
board.Add(new List<char>(){'-', 'R', '-', '-', '-', '-', 'Q', '-'});
board.Add(new List<char>(){'-', '-', '-', 'K', '-', '-', '-', '-'});
board.Add(new List<char>(){'-', '-', '-', '-', '-', '-', '-', '-'});
board.Add(new List<char>(){'-', 'P', '-', '-', '-', '-', 'p', '-'});
board.Add(new List<char>(){'-', '-', '-', '-', '-', 'p', '-', '-', });
board.Add(new List<char>(){'-', '-', '-', '-', '-', '-', '-', '-'});
board.Add(new List<char>(){'p', '-', '-', '-', 'b', '-', '-', 'q'});
board.Add(new List<char>(){'-', '-', '-', '-', 'n', '-', '-', 'k'});
initialise();
initTable();
int hashValue = computeHash(board);
Console.WriteLine("The hash value is : " + hashValue);
//Move the white king to the left
char piece = board[0][3];
board[0][3] = '-';
hashValue ^= ZobristTable[0][3][indexOf(piece)];
board[0][2] = piece;
hashValue ^= ZobristTable[0][2][indexOf(piece)];
Console.WriteLine("The new hash value is : " + hashValue);
// Undo the white king move
piece = board[0][2];
board[0][2] = '-';
hashValue ^= ZobristTable[0][2][indexOf(piece)];
board[0][3] = piece;
hashValue ^= ZobristTable[0][3][indexOf(piece)];
Console.WriteLine("The old hash value is : " + hashValue);
}}
// The code is contributed by Nidhi goel.
`