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Home * Engines * Fizbo

a Chess Engine Communication Protocol, and since version 1.5, UCI compliant [1] chess engine by Youri Matiounine - in October 2019 Fizbo 2 became open source. Fizbo was first released in May 2014 [2], apparently bitboard based, requiring x86-64 bitscan forward [3] and taking advantage from population count instruction. Since version 1.2, Fizbo performs a parallel search based on a version of enhanced PV splitting algorithm, only one split-point is active at a time, along with iterative deepening, since 1.3 with aspiration windows. Syzygy Bases with up to five pieces were used since version 1.4 released in May 2015. The transposition table with dense 8 byte entries is used also in quiescence search [4].

Further Versions

Fizbo 1.7

Fizbo 1.7, released in March 2016, improved in evaluation due to changed and new features, including pawn pattern, considering all possible combinations of two pawns of the same color [5], and further supports 6-piece Syzygy Bases.

Fizbo 1.8

Fizbo 1.8 in August 2016 came with a BMI2 executable, improved pondering logic, reworked parallel search logic, and multiple small changes to search and evaluation [6].

Fizbo 1.9

Fizbo 1.9, released on December 31, 2016, further enhanced considerably due to extensive changes and new features in evaluation [7].

Fizbo 2

Fizbo 2 was released in December 21, 2017 [8], and is apparently the last version by Youri Matiounine, who stopped working on the engine, and decided to release his source code on GitHub [9] [10] nearly two years later, featuring a two-layer neural network based evaluation with optional AVX2 intrinsics [11].

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