Maverick 0.5 Released!

You can download a new version of Maverick on the download page.

I’ve made quite a few changes since Maverick 0.5. 

  • Added more basic endgame knowledge
  • Added passed pawn evaluation (I think this added a lot of strength)
  • Beefed up the evaluation routine to include basic terms such as mobility
  • Fixed a nasty hash bug to do with mating positions
  • Added one-reply to check extensions in the first ply of the quiescent search (help with some tactics – little impact on playing strength)
  • Enabled hash cutoffs at PV nodes
  • Nodes per second have dropped considerably due to the slower evaluation (now between 3 million and 5 million on my 2.8 GHz i7 notebook)
  • A bazillion tweaks

How Strong is Maverick 0.5?

This is the first version of Maverick which I regards as reasonably strong.  In my tests it’s at least 200 ELO stronger than version 0.2.  If I had to guess I would say it’s about 2350 ELO on the CCRL rating scale.

Here are some test results:

[table align=”center” width=”800″ colwidth=”350|50|50|50″ colalign=”left|right|right|right”]

Match, Maverick, Opponent, Percentage(%)

Maverick 0.5 – Fruit 1.0,50.5,49.5,50.50%

Maverick 0.5 – Dragon 4.6,62.5,37.5,62.50%

Maverick 0.5 – Phalanx XXIII,57.5,42.5,57.50%

Maverick 0.5 – Tao 5.6,38.0,62.0,38.00%

Maverick 0.5 – TJchess 1.1U-x64,57.0,43.0,57.00%

Maverick 0.5 – Maverick 0.2 x64,75.5,24.5,75.50%

[/table]

All the games were played at 1 min per game on a 2.8 GHz Haswell i7 notebook.

Maverick only lost to Tao 5.6, a relatively old (2004) engine, but one I really like. Tao’s rating is about 2500 ELO so this results is expected.  I was surprised Maverick did so well against Dragon and Phalanx. I suspect their CCRL ratings of over 2350 ELO may be inflated.

Mate in 21:

I’ve used this simple position for many years to test hash tables. I first came across it in an advert for the Fidelity Mach III back in (circa.) 1988.  If a hash table is working as it should then an engine will have no problem finding c7, followed by an opposition king maneuver and the queening of the white pawn on b8.

Mate in 21

FEN: 2k5/8/1pP1K3/1P6/8/8/8/8 w – – 0 1

The previous version of Maverick could find c7 but when I added the hash cutoffs at PV nodes Maverick was able to find the mate in 21 in less than 10 seconds – I was pleased.

Next Developments:

I’m planning to release the next version when it can comfortably beat Tao 5.6, YACE and maybe Hermann 2.8. These engines are above 2500 ELO so it should take me a while.  My aim was to have a Maverick playing at 2500 ELO by Christmas – I think that’s still possible.  In the current version there is no king safety or selectivity apart from null move; so I think another 150 ELO by Christmas is possible.

Please met me know if you have any test results for Maverick or if you find a bug!

  • Marco Belli

    congratulations for this new release!!
    I hope our engine could compete in graham’s CCRL tournaments in few months, I think I’ll have to work hard to have Vajolet not overtaken by maverick 🙂

    • Steve Maughan

      Thanks Marco – it’ll be a while before Maverick get even close to the strength of Vajolet!

  • Excellent result Steve, what considerations did you use in hash cutoffs at PV nodes ?

    • Steve Maughan

      Hi Francesco – Thanks! Cut-offs at PV nodes are now handled the same as any other node. If there is an exact score with an appropriate depth in the hash table Maverick will recursively probe the hash table to find the principle variation. It seems to work well. Steve

  • Excellent improvement Steve!

    • Steve Maughan

      Thanks Erik – hopefully you’ll be able to improve MadChess and it will continue to be a good sparing partner for Maverick!