A KTM Quad 990 ATV 1
- A KTM Quad 990 ATV, custom-made from E-ATV Eicker Germany, Basevehicle was a KTM Supermotobike, Typ SM 990 with LC8 engine, Image by Stefan Krause, February 20, 2011, Wikimedia Commons↩︎
QBBEngine,
a didactic UCI compliant open source chess engine by Fabio Gobbato, written in C and published as single source file along with Pedone, which apparently uses a similar representation 1. The QBBEngine demonstrates the use of a compact quad-bitboard structure to represent the board, and further applies alpha-beta search and an evaluation based on static values and piece-square tables 2. The program performs a color agnostic move generation by flipping the board each time in make move.
Board-Definition
C Structure
/*
Board structure definition
PM,P0,P1,P2 are the 4 bitboards that contain the whole board
PM is the bitboard with the side to move pieces
P0,P1 and P2: with these bitboards you can obtain every type of pieces and every pieces combinations.
*/
typedef struct
{
TBB PM;
TBB P0;
TBB P1;
TBB P2;
uint8_t CastleFlags; /* ..sl..SL short long opponent SHORT LONG side to move */
uint8_t EnPassant; /* enpassant column, =8 if not set */
uint8_t Count50; /* 50 move rule counter */
uint8_t Rep; /* 0 if it's not a repetition, 1 if it is */
uint8_t STM; /* side to move */
} TBoard;Piece Coding
The board-definition with vertical nibbles as piece or empty square codes, i.e. the initial position:
| Square | 6 | 6 | 6 | 6 | 5 | 5 | 5 | 5 | 5 | ~ | 0 | ... | 0 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 3 | 2 | 1 | 0 | 9 | 8 | 7 | 6 | 5 | ~ | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| Piece | r | n | b | k | q | b | n | r | p | ~ | P | R | N | B | K | Q | B | N | R |
| PM | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ~ | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| P0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | ~ | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 |
| P1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | ~ | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 0 |
| P2 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | ~ | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 |
P2 RQK P1 NB K P0 P B Q PM side to move
1 . . 1 1 . . 1 . 1 1 . 1 1 1 . . . 1 1 . 1 . . . . . . . . . .
. . . . . . . . . . . . . . . . 1 1 1 1 1 1 1 1 . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 . . 1 1 . . 1 . 1 1 . 1 1 1 . . . 1 1 . 1 . . 1 1 1 1 1 1 1 1