Invictus

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[ Sol Invictus [1] Invictus, (InvictusChess, Invictus Chess)

an UCI compliant open source chess engine by Edsel Apostol, written in C++ and licensed under the GPL v3.0, first released in September 2018 [2]. Invictus is influenced by other open source engines in particular Stockfish, Ethereal, Defenchess, and Minic concerning Texel’s Tuning Method [3]. Tom Kerrigan of TSCP fame is given credit for sharing the Simplified ABDADA idea [4]. Invictus r324 had its tournament debut at TCEC Season 21 in May 2021 and gained a respectable 50% score in its strong Qualification League.

Board Representation

• Bitboards
• Magic Bitboards

PEXT Bitboards

Search

• Iterative Deepening
• Aspiration Windows
• Parallel Search using Threads
  • Simplified ABDADA
  • Shared Hash Table
  • NUMA Support
• Principal Variation Search
• Move Ordering
  • Internal Iterative Deepening
  • Killer Heuristic
  • History Heuristic
  • MVV/LVA
  • SEE
• Selectivity
  • Null Move Pruning
  • Late Move Reductions
  • Late Move Pruning
  • SEE Pruning
  • Futility Pruning
  • Quiescence Search

Evaluation

• Tapered Eval
• Material
  • Bishop Pair
• Mobility
• Pawn Structure
  • Open Pawns
  • Backward Pawn
  • Isolated Pawn
  • Doubled Pawn
  • Connected Pawns
  • Passed Pawn
• King Safety
  • King Tropism
  • Pawn Shelter
  • Pawn Storm
  • Attacking King Zone
• Tempo

Misc#

• Texel’s Tuning with Stochastic Gradient Descent using Adam
• Texel’s Tuning with Local Search

See also#

• Twisted Logic
• Hannibal

Forum Posts#

• Invictus chess engine r228 by Edsel Apostol, CCC, September 29, 2018
• Re: New engine releases 2019 (Invictus r305) by Edsel Apostol, CCC, December 05, 2019
• Re: New engine releases & news 2021 (Invictus r340) by Edsel Apostol, CCC, May 19, 2021
• Re: New engine releases & news 2021 (Invictus r382) by Edsel Apostol, CCC, June 07, 2021

External Links#

Chess Engine#

• GitHub - ed-apostol/InvictusChess: A state of the art chess playing engine
• Invictus in CCRL 40/15

Misc#

• invictus - Wiktionary
• Invictus (disambiguation) from Wikipedia
• Invictus from Wikipedia
• Oxford Book of English Verse 1250-1900/Invictus - Wikisource
• Virgin Steele - Invictus (1998), YouTube Video

References#

1. ↑ Sol Invictus, a Byzantine mosaic of a Zodiac Wheel — from the 6th century ancient Beth Alpha synagogue. Sol Invictus from Wikipedia, Wikimedia Commons
2. ↑ Invictus chess engine r228 by Edsel Apostol, CCC, September 29, 2018
3. ↑ 3.0 3.1 InvictusChess/README.md at master · ed-apostol/InvictusChess · GitHub
4. ↑ Simplified ABDADA by Tom Kerrigan

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