MadChess 3.0 Beta bef88d5 (Tweak Search, Tune Eval)

I’ll let my Pull Request notes (PR 3) explain where I began and where I finished (hint: not where I expected) with my latest code improvements to MadChess 3.0 Beta:

Originally, I intended this PR to add Static Exchange Evaluation (SEE) to MadChess’ search method to reorder or skip evaluation of captures and / or quiet moves that enable the opponent to profitably capture the most recently moved piece. After numerous attempts to write a method that evaluates piece exchanges- either statically (without actually moving pieces) or dynamically (move pieces and search), and integrate it into the search, I could not find any technique that improved the engine’s playing strength. I decided to leave in the Search.GetExchangeScore method (dynamic evaluation of piece exchanges) and associated exchangescore and analyzeexchangepositions UCI commands even though exchange score is not considered by the main search nor the quiet (quiescence) search.

I could not find any SEE technique that improved the engine’s playing strength.

In addition, this PR contains numerous tweaks to search logic and tuned evaluation parameters; and it contains numerous code performance and clarity improvements. Together, these changes account for a 30 Elo improvement in playing strength. MadChess 3.0 Beta, even with its primitive evaluation function (simple endgames, material, piece location, passed pawns, and piece mobility) now plays stronger (2450 Elo) than MadChess 2.2 (2443 Elo), at least at bullet time control.

1. GitHub commit (hash) or Subversion source code revision (integer)
2. Win At Chess position test, 3 seconds per position
3. Bullet chess, 2 min / game + 1 sec / move