Chess engine: Eubos 2.5

Eubos - a basic Java chess engine, written for kicks. Uses jcpi for the UCI protocol parts. Kind of weak, doesn't evaluate for king safety, for example. Now uses transpostion hashing, but because it runs in the Java VM on a bog standard PC, doesn't search very deeply (around 100K Nodes/s, though this is actually quite hard to evaluate due to the hashing). 

Author: Chris Bolt Rating CEDR=2736

v.2.5

This is mainly a release focused on delivering optimisation of the move generation and transposition hashing:

Reworked 3-fold draw checker to use an array based implementation indexed by ply, as opposed to a hash map keyed by Zobrist hash, this is more efficient.

Reworked the transposition table to use a primitive open hash set using the fastutils Java package (that is the reason for the increase in the size of the Eubs.jar file). This allows a more efficient linked hash map implementation, where the full hash table can be utilised (previously the hash utilisation varied between 35% to 80% based on the Transposition ageing).

Reworked the MoveList generation so that static arrays are used instead of dynamically creating and destroying objects at each node of the search.

However there are a few algorithmic changes:

Dumb7Fill based King Safety evaluation (scored as per the previous algorithm)

Allow transposition hits that are drawing due to three-fold to cause refutations (previously they were re-searched)

To install Eubos as an engine in Arena:
1. Select Engines > Install New Engine
2. In the file browser dialog that appears, change the drop down to *.bat
3. Navigate to the Eubos binary location, select the Eubos.bat
4. Select UCI protocol to communicate with Eubos
5. That's it! 

Eubos 2.5 download