Playing against a weaker CSTal

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chesstal
Posts: 3
Joined: Mon Jul 27, 2026 8:09 am
Full name: Adam Brown

Playing against a weaker CSTal

Post by chesstal »

Hi all

Because I wanted to play against CSTal and have some chance to beat it created a weakening wrapper - all AI under my directions.

zip file: https://murena.io/s/WXb2C3bemZbGtcJ.

1. wrapper.c is main code. I used Windows/mingw gcc to compile it:
gcc wrapper.c -o wrapper.exe -O2 -static -static-libgcc -static-libstdc++ -lm
2. wrapper.pdf explains code and how to use it.

Install wrapper.exe as a normal UCI engine.

Only did limited testing to calibrate - so it can be tuned more. But it works and produces results close to a weakened stockfish.

The code can weaken any engine by changing the engine name in wrapper.c and calibrating again.

I hope some of you find it useful and improve it further.
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Rebel
Posts: 7606
Joined: Thu Aug 18, 2011 12:04 pm
Full name: Ed Schröder

Re: Playing against a weaker CSTal

Post by Rebel »

I have read your PDF, it's a good system and indeed will work for many Stockfish versions also.
90% of coding is debugging, the other 10% is writing bugs.
Rowen
Posts: 128
Joined: Tue Nov 15, 2016 1:19 pm
Location: Cheshire, England

Re: Playing against a weaker CSTal

Post by Rowen »

chesstal wrote: Mon Jul 27, 2026 10:00 am Hi all

Because I wanted to play against CSTal and have some chance to beat it created a weakening wrapper - all AI under my directions.

zip file: https://murena.io/s/WXb2C3bemZbGtcJ.

1. wrapper.c is main code. I used Windows/mingw gcc to compile it:
gcc wrapper.c -o wrapper.exe -O2 -static -static-libgcc -static-libstdc++ -lm
2. wrapper.pdf explains code and how to use it.

Install wrapper.exe as a normal UCI engine.

Only did limited testing to calibrate - so it can be tuned more. But it works and produces results close to a weakened stockfish.

The code can weaken any engine by changing the engine name in wrapper.c and calibrating again.

I hope some of you find it useful and improve it further.
Hi
Is someone able to release a compiled version of this please?
chesstal
Posts: 3
Joined: Mon Jul 27, 2026 8:09 am
Full name: Adam Brown

Re: Playing against a weaker CSTal

Post by chesstal »

Rowen wrote: Tue Jul 28, 2026 10:41 am
Hi
Is someone able to release a compiled version of this please?
Hi Rowen

I didnt include the exe because of all the false virus problems Martin reported with Myracle. Anyway I have uploaded the exe : https://murena.io/s/5Q9fw7qtKT4DejM

It works on my windows machine. Hope it works for you.

Also tuning is optional - you can use wrapper with any engine by changing the engine name with the UCI option and using the default weakening values in the code.
chesstal
Posts: 3
Joined: Mon Jul 27, 2026 8:09 am
Full name: Adam Brown

Re: Playing against a weaker CSTal

Post by chesstal »

Rebel wrote: Mon Jul 27, 2026 11:50 am I have read your PDF, it's a good system and indeed will work for many Stockfish versions also.
Thanks for the comments Ed.

If you are interested I ran the same test with Rebel-EAS-3.0-AVX2 and the CSTal calibration.

1400: -0 Elo
1550: +23 Elo
1700: -17 Elo
1850: +49 Elo
2000: -12 Elo
2150: +2 Elo
2300: -7 Elo
2450: -51 Elo
2600: +21 Elo

So the default calibration weakens your engine well.