Chess engine: Renegade 0.9.0

Renegade is a chess engine written in C++ using Visual Studio 2019. It values readability and simplicity, and uses the UCI protocol to communicate, making it easy to connect it to chess frontends. Under construction since October 7, 2022 and released publicly on January 15, 2023.  

The project can be compiled using Visual Studio 2019 with C++20 features enabled. The engine makes heavy use of `popcnt` and `lzcnt` instructions, thus only processors from 2013 or so are supported, but the calls to these instructions are wrapped in a custom function, and replacing them with something more compatible is relatively straightforward. Currently only Windows binaries are compiled, but in the future I would like to make them for Linux as well.

v.0.9.0:

Speed improvements

Implemented magic bitboard lookups for sliding pieces

Reduced memory allocations in several places, again

Optimized variable types

New evaluation terms

Rooks on open and semi-open files

Knight outposts

More aggressive pruning

Null move pruning search reduced by 3 if depth > 6 (kept at 2 otherwise)

Razoring at depth 1 with margin of 300 cp (instead of 400)

Futility pruning extended to depth 3 with margin of 300 cp

Overhauled transposition table

Based on std::vector (no more std::unordered_map)

Replacement policy: always if hash is different, otherwise if depth is greater or equal

Stores depth and best move

Size calculated dynamically based on Hash parameter

Use debug hashalloc to show hash information

Added Clear Hash option

Not yet optimized (uses 24 bytes per entry)

Move ordering changes

Now based on MVV-LVA instead of material difference

Trying PV moves early only on the PV line

Uses the best move from the transposition table

Collecting more search statistics

First move beta cutoff rate, transposition table hit rate

Statistics are organized in its own struct

Updated method for node counting

Now incremented on SearchRecursive() and SearchQuiescence() calls (instead on evaluation)

Inflates node counts by about 25%

Evaluations are still counted and can be displayed by toggling ExtendedOutput

Better compatibility

Defaulting to statically linked libraries (shouldn't require external dll's)

Providing an exe that should work on older processors (untested, and it seems slightly slower)

Minor changes

New commands: debug isdraw (shows whether the position is a draw), debug plys (show game ply count), ch (shorthand for Clear Hash)

Simplified search code

Bugfixes

No longer draws in winning positions due to threefold repetitions (hopefully)

Fixed and expanded drawn game evaluation

Regression testing results: (time control: 10s+0.1)

Score of Renegade 0.9.0 vs Renegade 0.8.1: 1472 - 200 - 328  [0.818] 2000

...      Renegade 0.9.0 playing White: 744 - 77 - 179  [0.834] 1000

...      Renegade 0.9.0 playing Black: 728 - 123 - 149  [0.802] 1000

...      White vs Black: 867 - 805 - 328  [0.515] 2000

Elo difference: 261.1 +/- 16.8, LOS: 100.0 %, DrawRatio: 16.4 %

General notes:

The plan was to speed up the engine, both in nps terms, and make the search more efficient by applying more aggressive pruning to combat the low search depth. Both of these worked, more or less.

I've added a exe that hopefully should work with older processors, but I'm unable to verify this. I would like to support a wider range of systems in general, but it's a bigger challenge than I thought.

Feel free to ping me if there's any issues.

Rating CEDR=2271 Author - Krisztian Peocz

Individual statistics: Renegade 0.7.0 - 148 games (+ 17,=  5,-126), 13.2%

Critter 1.6a                  :   6 (+  0,=  0,-  6),  0.0 %

Houdini 1.5a                  :   2 (+  0,=  0,-  2),  0.0 %

Delocto 0.61n                 :   1 (+  0,=  0,-  1),  0.0 %

ECE 20.1                      :   2 (+  0,=  0,-  2),  0.0 %

Fritz 17                      :   2 (+  0,=  0,-  2),  0.0 %

Jinx 1.0                      :   1 (+  0,=  0,-  1),  0.0 %

Hiarcs 15.5                   :   2 (+  0,=  0,-  2),  0.0 %

Coiled 1.1                    :   2 (+  0,=  0,-  2),  0.0 %

Fritz 18                      :   2 (+  0,=  0,-  2),  0.0 %

Lc0 0.29.0                    :   2 (+  0,=  0,-  2),  0.0 %

Raven 1.30                    :   2 (+  0,=  0,-  2),  0.0 %

Peacekeeper 1.1               :   3 (+  0,=  0,-  3),  0.0 %

Akimbo 0.1.1                  :   2 (+  0,=  0,-  2),  0.0 %

BlackCore 5.0                 :   4 (+  0,=  0,-  4),  0.0 %

Stockfish 20230114            :   6 (+  0,=  0,-  6),  0.0 %

4ku 1.1                       :   2 (+  2,=  0,-  0), 100.0 %

Igel 3.3.0                    :   8 (+  0,=  0,-  8),  0.0 %

Inanis 1.2.0                  :   8 (+  0,=  2,-  6), 12.5 %

Koivisto 9.0                  :   4 (+  0,=  0,-  4),  0.0 %

Polyfish 230115               :   6 (+  0,=  0,-  6),  0.0 %

Caissa 1.5                    :   8 (+  0,=  0,-  8),  0.0 %

CorChess 20230114             :   2 (+  0,=  0,-  2),  0.0 %

Charisma Saphir               :   6 (+  0,=  0,-  6),  0.0 %

ShashChess 27.2               :   6 (+  0,=  0,-  6),  0.0 %

Koivisto 9.0 Ipman            :   8 (+  0,=  0,-  8),  0.0 %

Frozenight 6.0.0              :  10 (+  0,=  0,- 10),  0.0 %

Jangine 2023-01-15            :   8 (+  4,=  2,-  2), 62.5 %

Mess 0.0.2                    :   7 (+  2,=  0,-  5), 28.6 %

Clovis II                     :   4 (+  0,=  0,-  4),  0.0 %

Durandal 0.1.1                :   3 (+  3,=  0,-  0), 100.0 %

Princhess 0.9.0               :   5 (+  1,=  1,-  3), 30.0 %

Wasabi 1.5.0                  :   2 (+  0,=  0,-  2),  0.0 %

Sturddle 1.27                 :   4 (+  0,=  0,-  4),  0.0 %

Zagreus 2.0.0 alpha-2         :   4 (+  4,=  0,-  0), 100.0 %

Durandal 0.1.2                :   1 (+  1,=  0,-  0), 100.0 %

Sting Black Hole 4            :   2 (+  0,=  0,-  2),  0.0 %

Rapcschess 2022-12-08         :   1 (+  0,=  0,-  1),  0.0 %

Renegade 0.9.0 download