Table of Contents
Chess - Programming - Database
My propriety database format to hold a record of every move.
| Field | Bits | Range | Comment |
|---|---|---|---|
| Move From | 6 | A1=0, H1=7, A8=56, H8=63 | File=<file>-'A', rank=<rank>-'1'. Castle and Enpassant moves are assumed to be valid moves. |
| Move To | 6 | A1=0, H1=7, A8=56, H8=63 | File=<file>-'A', rank=<rank>-'1'. Castle and Enpassant moves are assumed to be valid moves. |
| Promotion Type | 3 | 000-111 | 000=unused, 001=Knight, 010=Bishop, 011=Rook, 100=Queen. |
| White Elo | 11 | 0-2047 | Actual elo of white – 1000. |
| Elo Diff | 8 | 0-255 | 0-255=w, 256-511=b. |
| Elo Diff Neg | 1 | 0-1 | 0=positive, 1=negative. |
| %WDL | 9 | 0-511 | 0-99=Percentage Win, 100-199=Percentage Draw, 200-299=Percentage Loss. From White Perspective. Unused Values 300-511. |
| Count | 12 | 0-4095 | Rolling. |
| Weight | 8 | 0-255 | A measure for the likelihood of a win after that particular move has been made. 0-127=w, 128-255=b. Default is to use ELO changes to calculate this. |
NOTE: A total of 64-bits.
Moves
Moves are stored in format:
- A1 = 0, H1 = 7, A8 = 56, H8 = 63.
- File = <file> - 'A', row = <rank> - '1'.
- Castle and Enpassant moves are assumed to be valid moves.
Promotion Type
Assumed that the associated moves are for a pawn and this promotion is valid.
White Elo
The average of the ELO rating for the White player - 1000.
Elo Diff & Elo Diff Neg
Used to calculate the ELO rating of the Black Player.
Either add, or subtract this figure from the White Elo.
- If Elo Diff Neg is set, then subtract, otherwise add.
%WDL
The percentage of Wins, Draws and Losses for the White Player.
- Obviously, the Black Player would be the opposite.
| Values | Description |
|---|---|
| 0-99 | Percent of Wins. |
| 100-199 | Percent of Draws. |
| 200-299 | Percent of Losses. |
| 300-511 | Unused Values. |
Count
The number of games having played this move.
A maximum of 4096 games is recorded.
The other fields using this figure for their calculations, such as %WDL, should be recalculated / updated even though this maximum number of 4096 is reached.
Weight
A measure for the likelihood of a win after that particular move has been made.
Range is 0-255.
Default is to use ELO changes per this formula:
white_probability = (1.0 / (1.0 + std::pow(10.0, ((rating1 - rating2) / 400.0)) ) );
black_probability = 1 - white_probability;
if (rating1 > rating2)
{
result=-black_probability/20;
}
else
if (rating1 < rating2)
{
res=white_probability/20;
}
NOTE: A bespoke formula could be used to update this weighting.
- Instead of using the k factor/value of 400 that the original formula uses, this is changed to be 100 + ((score difference) * 2).
- So the max k factor would be 140 (20-0 is the biggest win, multiply by 2, add to 100).