Linux Binaries for Maverick 1.5

Thanks to Antonio Arias we now have Linux binaries included with the main distribution of Maverick. You can download them here.


Maverick 1.5 (Leiden WCCC 2015) Released

I’m happy to announce the release of Maverick 1.5. This is close to the version which competed in the 2015 World Computer Chess Championship in Leiden. I’d estimate that it’s only about +50 ELO better than version 1.o (based on self play). I’m about to embark on a rewrite of the evaluation function so I thought it a worthwhile launch.

The main changes are:

  • Tweaks to the piece square tables (especially pawns)
  • Added endgame knowledge
  • Less selectivity
  • Fixed a quiescent search bug which unnecessarily research some moves

You can download it below or from the Download Page. I’ve only included a 32 bit and 64 bit version which should work on most systems. If anyone would like to create a Linux / Apple Mac compile then I’d be happy to include it in with this version. The source is available here

Pictures from Leiden 2015


New Engine – The Baron

I’m delighted to host another new engine at The Baron recently played at the WCCC in Leiden. It was operated by Richard’s delightful daughter Tessa. I’m not sure of the exact playing strength of The Baron but it’s certainly strong. It’s a full feature engine with SMP support and a comprehensive evaluation function. This version dates back to February 2012.  You can find out more on The Baron’s own page.



World Computer Chess Championship 2015

This week I’m in Leiden for the World Computer Chess Championships. I’ll try to blog about it. Here’s a quick pre-tournament video:

You can see Maverick’s screen and a video link here (maximum of 50 people):




Python Chess

I’m delighted to give you this guest post by Niklas Fiekas, the creator of Python Chess. You may think Python Chess is just another chess engine. It isn’t. It’s a library of routines which can manipulate and analyze chess data using Python.  After I learnt about Python Chess I immediately went to Code Academy and took their course on Python. I really see this set of tools becoming a key part in any testing or development frame-work.

Over to Niklas…

Python-chess by example: Automating the Bratko-Kopec Test

Decades ago (1982) Kopec and Bratko published a systematic test for assessing the strength chess-playing programs (pdf). Despite its age it can still be fairly challenging, even for modern chess engines. Of course 24 test positions are not going to be enough for a definite result, especially given that most positions are of a specific type: fairly closed and the solution often involves some kind of sacrifice.

For each of the 24 positions a unique best move is known. The engine is given 120 seconds to solve each position. 1 point is awared for the correct best move.

The positions are given as EPDs. In this article we are going to automate the process of testing an UCI engine, introducing python-chess along the way.


Why Python (and python-chess)?

When it comes to chess programming, C++ often is the language of choice. Performance is critical. Not nescessarily so, in this case. All intensive calculations will be done by the engine. We just want to convert the given EPD lines, send them to the engine and handle its response. Python is a very good tool for high-level stuff like this (or making a mini chess computer, or making a website to probe tablebases or creating a cross platform chess GUI). We will use python-chess to deal with the chess rules and the involved formats: EPDs, FENs and the UCI protocol. python-chess can also read and write PGNs, read Polyglot opening books and probe Syzygy tablebases.

Chess positions

FEN: 1k1r4/pp1b1R2/3q2pp/4p3/2B5/4Q3/PPP2B2/2K5 b – – 0 1

BK.01 is one of the easier positions: Black to move and mate in 3

In python-chess a position is represented by a chess.Bitboard(). To create a position from a FEN:

You can then check if a specific move is legal:

Or to get the shorter SAN notation of the move:

Or to make a move and see if it is a check (and much more):

Here we are just going to parse an EPD line to setup a position and get the related info:

Communicating with an UCI engine

Next we will communicate via UCI with a chess engine like Maverick. First start the engine process:

The engine expects an initial uci command. Then it will send information about its identity and options.

Now setup the position:

And calculate for two minutes. The result is the best move (according to the engine) and an optional ponder move (the expected reply the engine wants to ponder on).

Or in fact comparing it with the expected best move from the EPD:


Putting it all together

Congratulations Maverick 0.51 x64! On my machine you score 18/24, which is almost on a par with Stockfish 6 64’s 19/24.



The original Brato-Kopec test has one more rule: Sometimes the engine changes its mind. If it had the solution at the 30, 60 or 90 second mark but then discarded it, 1/4, 1/3 or 1/2 points are awarded. In order to do this we need to look at the engines principal variations while it is thinking. This is included in the full code of this example.

You can find out more about Python Chess at


Maverick 1.0 Released

I’m pleased to be able to release Maverick 1.0. This version adds considerable selectivity to the search. It has a basic implementation of Late Move Reduction and Beta pruning. In my tests it is about 2500 ELO on the CCRL scale, so it’s time to give it the 1.0 version number.

A full list of changes are:

  • Added Late Move Reduction
  • Added beta pruning (inspired by Senpai)
  • Added unstoppable pawn code
  • Added king and pawn endgame knowledge
  • Added knight outpost bonus
  • Added refutation moves to the move ordering

There are also ARM and Linux version included for the first time (thanks Jim Ablett)

I’m pleased with the style of play. Maverick aggression coupled with its positional naivety makes for interesting play! If you play against chess engines I’d be interested in any feedback.

You can download Maverick 1.0 from the Download Page


Maverick 0.60 Released

Today I’m releasing Maverick 0.60. The main changes are as follows:

  • Added support for Chess960
  • Added basic king safety (this makes the playing style much more attractive)
  • Fixed a problem with using the opening book with Arena
  • Fixed an obscure bug which could crash the engine after a stop command
  • Transferred source code to Github (
  • Made a bazillion tweaks which may, or may not, help!

In self play matches against 0.51 it shows an improvement of about 50 ELO. I’m hoping this will translate to a real-world strength increase of at least 30 ELO.

I’m now about to start working on improving the selective search!

You can download it on the download page


Free Version of Visual Studio Professional 2013

Last week Microsoft release a Community Edition of Visual Studio 2013.  This is a free version of the Professional edition of Visual Studio 2013. Previously Microsoft’s free edition was Visual Studio Express. This only compiled to 32 bit and didn’t include a Profiler or Profiler-Guided-Optimization.  The new Community Edition includes all of these goodies and can generate 64 bit executables.  This is a big deal for chess programmers. It means you can easily develop and test your engine from within the same high quality development environment (I know we’ve always had GCC but this is more integrated than the mishmash of open source tools).

There are some constraints on who can use the Community Edition. You can only use it if your engine isn’t commercial, or if it brings in less than $1 million per year – I’m sure that covers every chess engine developer!!

You can find out more and download here.

The Holiday season is coming. I’m hoping to have more time to dedicate to chess programming. For the last six months I’ve been swamped with work – but I think there is a light at the end of the tunnel. More updates to come.


Two New Engines Hosted on

I’m excited to let everyone know about two new engines which are to be hosted on this blog.

The first engine is Fruit Reloaded. This is fork of Fabien Letouzey’s Fruit 2.1.  Most of the new development (including SMP search) has been done by Daniel Mehrmann and Ryan Benitez.  You can find out more here:

The second, engine is a big surprise. Fabien himself has been dabbling once again in chess programming. He’s come up with a brand new engine – Senpai!  It’s a bitboard engine (Fruit was array based) with SMP search. I ran some quick tests on a beta version and Senpai 1.0 drew a 150 game match against Chiron 2.0. Although this is a small sample of only one engine, it implies a rating of approximately 3100 ELO on the CCRL scale.  You can find out more about Senpai here:

Let the fun begin!