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This release increases the playing strength of Defenchess significantly. Below are every change introduced in this version.


  • Revised time management for X/Y and X+0 (moves per time and zero increment) time controls
  • Opposite colored bishops endgame knowledge
  • Slight improvements in how time is counted and PVs are printed while failing high/low (now at least one move will always be printed even when failing)
  • Improved thread management (fixed a bug where not providing a position after setting the number of threads would crash the engine)
  • Improved draw (and lack thereof) detection
  • Fixed an issue where TB scores would never be returned
  • Fixed a bug in calculating pinned piece mobility
  • Allowed pinned pieces to capture pieces of equal or higher value in mobility calculation
  • Implemented followup history
  • Fixed a bug that prevented extensions from being applied in the first moves searched in PV nodes
  • Introduced king threats against pieces and pieces flanking the king in evaluation
  • Introduced the use of history in late move reductions
  • Tweaked endgame scores for the side with higher material but no pawns
Assets 5

@cetincan0 cetincan0 released this Jul 25, 2019 · 1 commit to master since this release

Major tuning overhaul and a TB bug fix.


  • Significant ELO gains were obtained by using the training set created by the author of Zurichess which can be found at
  • Fixed an obscure TB bug where Defenchess would play an illegal move when playing as black with a black pawn on the B2 square.
  • The quit command should quit without crashing the engine now.
  • Added a no popcount binary for Windows.

Please let me know if you notice any issues. Thanks!

Assets 5

@cetincan0 cetincan0 released this Jul 23, 2019 · 4 commits to master since this release

Defenchess 2.0 release. Windows and Linux binaries are included.

Assets 4
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