Differences

This shows you the differences between two versions of the page.

--- chess:programming:database [2022/01/11 09:59] – created peter
+++ chess:programming:database [2022/01/11 10:50] (current) – peter
@@ Line 1: / Line 1: @@
 ====== 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.|
+<WRAP info>
+**NOTE:**  A total of 64-bits.
+</WRAP>
+----
+===== 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:
+<code>
+  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;
+  }
+</code>
+<WRAP info>
+**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).
+</WRAP>
+----
 [[Chess:Programming:Database|Database]]