OpenChess

Official compiles
As usual, 4 compiles available, 64-bit only

• Linux SSE 2: discocheck_4.3_sse2
• Linux SSE 4.2: discocheck_4.3_sse4.2
• Windows SSE 2: discocheck_4.3_sse2.exe
• Windows SSE 4.2: discocheck_4.3_sse4.2.exe

SSE 4.2 is faster, but only works with recent CPUs. Try it first, and if it fails, use SSE 2 as a fallback.

What's new

• bugfix: pawn hash table was not working (fixing this was a major speedup, although a non functional change)
• simplify IID condition: now much less dependant on the predicted node type.
• bugfix: mate scores were adjusted when being read from the TT, but not before being written. Thanks to Marco Costalba for spotting this bug.
• only set ep-square when it can be attacked by enemy pawns.
• apply double reductions a little bit earlier at predicted Cut nodes.
• reduce max depth from 8 to 6 for move count pruning.
• rook pair penalty (redundancy).
• increase king safety penalty when the king is advanced and cannot retreat.
• improved hanging pieces asymmetric evaluation.
• do not sort predicted All nodes differently.
• improved stand pat stuff in qsearch and search, using a separate asymmetric evaluation.
• unify scoring of passed and candidate passed pawns, for better eval continuity.
• tweak passed pawns scoring.
• improved the formula of ELO levels.
• skip SEE pruning and LMP at the Root node.
• lots of code cleanup.

ELO ?
Based on my estimations, it should be around 2800 CCRL.

Enjoy!

Thanks