[SPORK-108] Switch from WDL->DTZ for endgame

[michelle-lai-swl]

Change from WDL to DTZ scores for endgame tablebases (syzygy)

• This is done to aim to avoid repetition. See the linked issue. Moreoever, it allows more precise handling of endgame outcomes (WIN, CURSED_WIN, LOSS, etc...) found within the tablebase, at the expense of more filesystem space (which is usually readily available).
• Implements an algorithm to check desirability of DTZ category (unconditional loss last, unconditional win first).
  • If DTZ category is higher than previous move, select the new category.
  • If DTZ category is same as previous move, compare against the previous score (depending on the category) and change the move if required.

[KYLChiu]

We need to check for cursed win/loss too. Will do.

[ccjeremylo]

Change from WDL to DTZ scores for endgame tablebases (syzygy)

• We now handle all cases, from loss to win, given it can be probed in the table base.

• Implements an algorithm to check desirability of DTZ category (unconditional loss last, unconditional win first).

  • If DTZ category is higher than previous move, select the new category.
  • If DTZ category is same as previous move, compare against the previous score (depending on the category) and change the move if required.

@KYLChiu suggest adding a line here to clarify context - why we decided to change from WDL to DTZ - see here for official doc

[KYLChiu]

Change from WDL to DTZ scores for endgame tablebases (syzygy)

• We now handle all cases, from loss to win, given it can be probed in the table base.

• Implements an algorithm to check desirability of DTZ category (unconditional loss last, unconditional win first).

  • If DTZ category is higher than previous move, select the new category.
  • If DTZ category is same as previous move, compare against the previous score (depending on the category) and change the move if required.

@KYLChiu suggest adding a line here to clarify context - why we decided to change from WDL to DTZ - see here for official doc

Not enough to check the linked issue? ;) Anyway, done.

[ccjeremylo]

Change from WDL to DTZ scores for endgame tablebases (syzygy)

• We now handle all cases, from loss to win, given it can be probed in the table base.

• Implements an algorithm to check desirability of DTZ category (unconditional loss last, unconditional win first).

  • If DTZ category is higher than previous move, select the new category.
  • If DTZ category is same as previous move, compare against the previous score (depending on the category) and change the move if required.

@KYLChiu suggest adding a line here to clarify context - why we decided to change from WDL to DTZ - see here for official doc

Not enough to check the linked issue? ;) Anyway, done.

Please excuse my blindness, but ty for clarifying 🤓