I’m currently trying to develop a chess engine in C#.
Thanks to the detailed answers given to me in my previous thread, I’m now studying how to apply a bitboard system to my game structure.
In principle, I’m trying, again, to apply some Object oriented design to this new concept of engine, but now I have some unanswered questions in mind:
-
I would like to implement a bitboard structure leaning on a UInt64 field to abstract that concept, maybe providing methods like GetFirstBit() or Shift(..) or even PopCount(..), but I don’t know how that would influence performance and memory allocation. Would be better a class to increase performance thanks to reference copy, or for a so small object the Heap would just complicate things?
-
I would even implement an indexer to enter on single bits like in a normal array, would it a waste of resources or it is a good idea (for a chess engine) ?
-
I’m trying to minimize changes to my project, but I realized that all my piece hierarchy and my Move and Square classes would be set aside and never used more… Should I just give up that design, or can I reuse those classes somehow?
This is a prototype of what i would like to implement into my engine:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Chess_Engine___NOGUI
{
public struct BitBoard
{
public UInt64 bitBoard;
public BitBoard(UInt64 board)
{
bitBoard = board;
}
public static implicit operator BitBoard(UInt64 board)
{
return new BitBoard(board);
}
public static implicit operator UInt64(BitBoard board)
{
return board.bitBoard;
}
public static BitBoard operator <<(BitBoard board, int shift)
{
return board.bitBoard << shift;
}
public static BitBoard operator >>(BitBoard board, int shift)
{
return board.bitBoard >> shift;
}
public static BitBoard operator &(BitBoard a, BitBoard b)
{
return a.bitBoard & b.bitBoard;
}
public static BitBoard operator |(BitBoard a, BitBoard b)
{
return a.bitBoard | b.bitBoard;
}
public static BitBoard operator ^(BitBoard a, BitBoard b)
{
return a.bitBoard ^ b.bitBoard;
}
public static BitBoard operator ~(BitBoard a)
{
return ~a.bitBoard;
}
}
}
And Here the classes that i would like to save…
this is my Move class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Chess_Engine___NOGUI
{
class NullMove : Move
{
public NullMove()
: base(null, null, null)
{
}
}
class Move
{
public string Algebraic
{
get
{
return ToAlgebraic();
}
} // JUST FOR DEBUG
public Square FromSquare { get; set; }
public Square ToSquare { get; set; }
public Piece PieceMoved { get; set; }
public Piece PieceCaptured { get; set; }
public PieceType PiecePromoted { get; set; }
public bool HasPromoted
{
get
{
return PiecePromoted != PieceType.None;
}
}
public bool IsEnpassant { get; set; }
public bool HasCaptured
{
get
{
if (PieceCaptured != null)
return true;
else
return false;
}
}
public bool IsCastling
{
get
{
return IsLongCastling || IsShortCastling;
}
}
public bool IsLongCastling
{
get
{
if (PieceMoved is King)
{
if (FromSquare.X - ToSquare.X == 2)
return true;
else
return false;
}
else
{
return false;
}
}
}
public bool IsShortCastling
{
get
{
if (PieceMoved is King)
{
if (FromSquare.X - ToSquare.X == -2)
return true;
else
return false;
}
else
{
return false;
}
}
}
public bool IsCheck { get; set; }
public bool IsCheckMate { get; set; }
public bool IsDoublePawnPush
{
get
{
if (PieceMoved.Type == PieceType.Pawn)
if (!HasCaptured)
if (ToSquare.X == FromSquare.X)
if (SideMove == PieceColor.White)
{
if (ToSquare.Y - FromSquare.Y == 2)
return true;
}
else
{
if (ToSquare.Y - FromSquare.Y == -2)
return true;
}
return false;
}
}
public PieceColor SideMove
{
get
{
return PieceMoved.Color;
}
}
public Piece RookMoved { get; set; }
public Square KingPosition { get; set; }
public Square RookPosition { get; set; }
public float Score { get; set; }
public Move(Square fromSquare, Square toSquare, Piece pieceMoved, PieceType piecePromoted = PieceType.None)
{
this.FromSquare = fromSquare;
this.ToSquare = toSquare;
this.PieceMoved = pieceMoved;
this.PiecePromoted = piecePromoted;
}
public static bool operator ==(Move a, Move b)
{
return a.Equals(b);
}
public static bool operator !=(Move a, Move b)
{
return !a.Equals(b);
}
public override bool Equals(object other)
{
if (other is Move)
{
Move compare = (Move)other;
return (this.FromSquare == compare.FromSquare && this.ToSquare == compare.ToSquare);
}
else
{
return false;
}
}
public override int GetHashCode()
{
return base.GetHashCode();
}
public string ToAlgebraic()
{
StringBuilder algebraic = new StringBuilder();
if (IsCastling) // se e` una mossa di arrocco
{
if (IsShortCastling)
algebraic.Append("O-O"); // arrocco corto
else
algebraic.Append("O-O-O"); // arrocco lungo
}
else
{
algebraic.Append(FromSquare.ToAlgebraic());
if (HasCaptured)
algebraic.Append("x"); // cattura
algebraic.Append(ToSquare.ToAlgebraic());
}
if (HasPromoted)
algebraic.Append(PiecePromoted.GetInitial());
if (IsCheck)
if (IsCheckMate)
algebraic.Append("#"); // scacco matto
else
algebraic.Append("+"); // scacco
return algebraic.ToString();
}
}
}
Here is my Square class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Chess_Engine___NOGUI
{
sealed class Square
{
public int X { get; set; }
public int Y { get; set; }
public Square(int x, int y)
{
this.X = x;
this.Y = y;
}
public static implicit operator Square(string str)
{
// converte la notazione algebrica (es. a1) in coordinate decimali
str = str.ToLower(); // converte la stringa in minuscolo
int x = (int)(str[0] - 'a');
int y = (int)(str[1] - '1');
return new Square(x, y);
}
public static bool operator ==(Square a, Square b)
{
if (System.Object.ReferenceEquals(a, b))
{
return true;
}
if (((object)a == null) || ((object)b == null))
{
return false;
}
if (a is Square)
{
Square compare = (Square)b;
return (a.X == compare.X && a.Y == compare.Y);
}
else
{
return false;
}
}
public static bool operator !=(Square a, Square b)
{
return !(a == b);
}
public override bool Equals(object obj)
{
return base.Equals(obj);
}
public override int GetHashCode()
{
return base.GetHashCode();
}
public string ToAlgebraic()
{
string str = "";
str += (char)(this.X + 97);
str += (this.Y + 1).ToString();
return str;
}
}
}
and here is my abstract Piece class:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Chess_Engine___NOGUI
{
public enum PieceType { None, Pawn, Knight, Bishop, Rook, Queen, King }
public enum PieceColor { None, White, Black }
public static class Extensions
{
public static PieceColor GetOpposite(this PieceColor color)
{
if (color == PieceColor.White)
return PieceColor.Black;
if (color == PieceColor.Black)
return PieceColor.White;
else
return PieceColor.None;
}
public static char GetInitial(this PieceType type)
{
switch (type)
{
case PieceType.Bishop:
return 'B';
case PieceType.King:
return 'K';
case PieceType.Knight:
return 'N';
case PieceType.Pawn:
return 'P';
case PieceType.Queen:
return 'Q';
case PieceType.Rook:
return 'R';
default:
return ' ';
}
}
}
abstract class Piece
{
public char Notation { get; set; }
protected List<Move> movesList;
public Square startingSquare { get; set; }
public Square square { get; protected set; }
public Square lastSquare { get; set; }
public PieceType Type { get; set; }
public PieceColor Color { get; set; }
public virtual bool AlreadyBeenMoved
{
get
{
return square != startingSquare;
}
}
public Piece(Square square, PieceColor color)
{
this.startingSquare = square;
this.square = square;
this.lastSquare = square;
this.Color = color;
this.movesList = new List<Move>();
}
public void Move(Square destination)
{
square = destination; // aggiorna la posizione attuale
}
public bool ShouldUpdateMoves()
{
if (lastSquare == square) // se il pezzo non si e` mosso
{
if (movesList.Count > 0)
return false;
}
else
{
lastSquare = square;
movesList.Clear();
}
return true;
}
public abstract List<Move> GetMoves();
}
}
I would like to emphasize that some really important factors for a correct answers here are speed optimization and well object oriented design.
thanks to all 🙂
At the end of your question, you specify 2 factors that fundamentally conflict with each other. My recommendation is that you focus on one or the other. Either you value good OO design or you value good performance. You can’t really have both.
To answer the question in your first bullet point, I personally don’t use any OO for finding (for example) the first significant bit in a bitboard:
I don’t use Piece or Square classes:
I do use a Move class, but it should probably be a struct. My tests didn’t show a significant difference: