Shield Chess Engine

Shield is an UCI chess engine written in the D programming Language.

It is my third chess engine after Tamerlane and Madeleine and I started working on it around November 2015.

History

16/01/2018 - Shield 2.1 (~2840+ ELO)

Fixed an issue with the UCI protocol, now Shield loads correctly into Fritz GUI.
Added some knowledge for KBPvK endgames.
Corrected time management, now Shield should allocate more time for the search (more specifically in a "game in X" game).
Slightly reworked the logic Shield uses to select a move from the opening book.
Added SEE pruning in main search.
Added hidden passers evaluation and reworked evaluation of passed pawns, plus some other minor change.
Corrected a bug in opposite colour bishop ending.
Added an extension to Polyglot opening books to store statistics about each opening line. The book generation routine of Shield (--genbook command line parameter) was modified to generate also the statistics file.
Added some configuration parameter as UCI option (see section "UCI Options" for more details).

22/11/2017 - Shield 2.0 (~2700+ ELO)

Complete new version! Total rewrite of Shield code.
Support for Polyglot opening books (old Shield 1.x book format is no longer supported).
Support for multi-thread search up to 16 cores.

25/09/2016 - Shield 1.3.1 (~2500+ ELO)

04/09/2016 - Shield 1.3 (~2500+ ELO)

Some "raw speed" enhancements: nps is greatly improved.
Changed History Heuristic and added configuration parameters.
Completly removed PST tables (left only the table for King).
Added new evaluation configuration parameters:
- Endgame piece values (currently no difference with middlegame values, but can be changed).
- Added the possibility to specify the middlegame and endgame values for most of the evaluation terms (some tuning is still needed !!)
- Added "MaterialIncidence" configuration parameter to change the importance of "material" on the evaluation function.

20/03/2016 - Shield 1.2 (~2450+ ELO)

Added pondering
Added singular move extension
Changed futility pruning algorithm and added new configuration parameters
Revisited Piece values
Added some new configuration evaluation parameter
Internal rework of some classes to better use D template capabilities
Slighlty better understanding of opposing colour bishop endgames
Slightly better endgame knowledge (now Shield should know how to play KBNk, KBBk, KQkr, KRBkr, KRNkr endgames)
Somehow tuned evaluation parameters
Added preliminary King Safety
New opening book.

10/01/2016 - Shield 1.1 (~2350+ ELO)

Added piece values in configuration
Added experimental Static Nullmove Pruning
Added some small new evaluation terms:
- Connected/Supported passed pawns
- King not castled/castle loss penalities
- Pinned pieces penalities
- Control of weak central squares
- Fianchetto bishops Bonus
Added some book configuration options.
Removed/changed some old configuration options.
Corrected a nasty configuration bug (array parameters were wrongly used!!!).
Some minor tweaks on the search
Now Shield comes with its own book. You can specify the name of the book Shield will use by using the new UCI Book parameter.
The default book was generated with default parameters using CCRL 40/40 games
Added the possibility to generate an opening book from a list of PGN files. Launch "Shield.exe --help" to view possible parameters.
Added a simple interactive book viewer (only view, no manual editing for the moment). Launch "Shield.exe --showbook".
NOTE: the moves are ordered by score (what you see with K=...). That score is the number represented by the new BookScoreValue configuration parameter
Multicut is removed
Quiescence pruning is removed.

22/12/2015 - Shield 1.0 (~2150+ ELO)