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Lichess blog: Fat Fritz 2 is a rip-off

A few days ago, ChessBase released Fat Fritz 2, described on their website as the "new number 1" chess engine "with a massive new neural network, trained by Albert Silver with the original Fat Fritz."

They advertise Fat Fritz 2 as using novel strong ideas compared to existing chess engines, but in reality Fat Fritz 2 is just Stockfish with a different neural network and minimal changes that are neither innovative nor appear to make the engine stronger.

As this is not the first time something like this has happened involving both ChessBase and A. Silver, we would like to share our impression of these releases.

See full Lichess blog:

Open Source Community Critical Of Chessbase, Fat Fritz 2

The development teams behind the two most successful and influential open-source chess programs, Stockfish and Leela Chess Zero, have issued statements denouncing the commercial program Fat Fritz 2 and the company Chessbase that is selling the program for 99,90 euros.

The statements (Stockfish blog, lichess announcement) assert that the engine in Fat Fritz 2 is Stockfish with minimal changes, that Fat Fritz 2 has violated the GNU General Public License under which Stockfish is released, and that Chessbase's marketing has made false claims about Fat Fritz 2's playing strength.

See full article

Official test by SF team, at fishtest conditions, of Stockfish 13 vs the sold version of CB/AS (ff2) net and the corresponding Stockfish player.

TC 10+0.1: PGN

../ordo -a 0 -p out-sf13-vs-ff2-TC10+0.1.pgn -A sf13 -s 100 -q  -J -D -W

    1 sf13      :     0.0   ----  34445.5   65536    53     100
    2 ff2       :   -18.1    1.3  31090.5   65536    47     ---

White advantage = 29.29 +/- 0.67
Draw rate (equal opponents) = 77.35 % +/- 0.18

TC 60+0.6: PGN

../ordo -a 0 -p out-sf13-vs-ff2-TC60+0.6.pgn -A sf13 -s 100 -q  -J -D -W

    1 sf13      :     0.0   ----  33774.0   65536    52     100
    2 ff2       :   -10.8    1.0  31762.0   65536    48     ---

White advantage = 24.72 +/- 0.50
Draw rate (equal opponents) = 87.77 % +/- 0.14

Setup and parameters

Same setup as fishtest, using 8moves_v3.pgn book, run in 128 batches
(command used for TC 60+0.6):

../cutechess-cli \
    -repeat -rounds 1 -games 512 -tournament round-robin \
    -srand $RANDOM -resign movecount=3 score=400 \
    -draw movenumber=34 movecount=8 score=20 -concurrency 64 \
    -openings file=../8moves_v3.pgn format=pgn order=random plies=16 \
    -each tc=60+0.6 option.hash=64 proto=uci -ratinginterval 128 \
    -engine cmd=../stockfish.sf13 name=sf13 \
    -engine cmd=../stockfish.ff2 name=ff2 \
    -pgnout out-sf13-vs-ff2.pgn

Compiled using exactly the same compiler and same settings

on master at SF13 commit

make clean && make -j ARCH=x86-64-avx2 profile-build
mv ./stockfish ./stockfish.sf13
./stockfish.sf13 bench 2>&1 | grep "Nodes searched"
Nodes searched  : 3766422

on ff2 branch with the correct CB/AS net added to the src directory

make clean && make -j ARCH=x86-64-avx2 profile-build
mv ./stockfish ./stockfish.ff2
./stockfish.ff2 bench 2>&1 | grep "Nodes searched"
Nodes searched  : 4025201

ChessBase’s Fat Fritz 2 condemned as ‘rip-off’ Stockfish clone

Stockfish and Leela Chess Zero developers have joined together with Lichess to condemn what they see as false advertising by ChessBase of the recently released Fat Fritz 2 chess software. The promotional material suggests the chess engine included with the software is “the new number 1”, and that the key contribution is Albert Silver’s in training its neural network. The Stockfish developers, meanwhile, point out that Fat Fritz 2, which is being sold for around 100 euros, is the free Stockfish with a net that adds no noticeable increase in playing strength.

See full Chess24 blog

Fat Fritz II and Stockfish- A Computer Chess Controversy

Anyone who's been paying any attention to chess Twitter or Twitch in the past few days will have heard of Fat Fritz II, the new chess engine from ChessBase and Albert Silver. They also will know that it's ignited a controversy that's spread well beyond the insular computer chess community.

Seriously, how often do GM Hikaru Nakamura and GM Anish Giri mention the Stockfish developers on Twitter?

What is Fat Fritz II? What does Stockfish have to do with this? And why is everyone so angry? That's what I'm here to explain!

See full the_real_greco's blog

Fat Fritz 2 – Ein unmoralisches Angebot

Stockfish 13 und der fette Fritz