Phalanx Reborn...and we really mean it this time! (Phalanx XXIII)

Summary: Phalanx XXIII isn't strong enough for cutting-edge analysis (2400+), but it's a nice engine to play against for fun.

Phalanx has been around for a while, but in the past I've had a hard time recommending it as a playing opponent. At the weak levels where I live, it moved instantly, and I found that a bit unnerving...So it never really made it to my short list. The engine's programmer, Dušan Dobeš, abandoned the project around 2000, so I figured we'd never see a new version. In 2006, Phalanx was resurrected by José de Paula Rodrigues and Jim Ablett (Phalanx Reborn), but it was mostly just the same old Phalanx.

Well, after a fourteen-year hiatus, Dušan's back...with a new version, Phalanx XXIII. And the new version no longer moves instantly at the low levels! Phalanx has a reputation for having an attractive playing style. According to Dušan, it's a "slow thinker" with lots of chess-specific knowledge.

Phalanx XXIII does have some quirks, but nothing I consider serious. It's only about a 2400+ elo engine, so if you're looking for a GM+ engine, look elsewhere.

It's a Winboard engine, so your GUI must be able to install Winboard engines. Also, most Winboard engines use configuration files for the engine settings, but Phalanx uses command-line switches instead of a configuration file. (Most GUIs have a place to enter engine command-line switches.)

The easy levels go from e1 to e99. The Phalanx README file states, "1 is the easiest and 99 is the hardest easy level". However, it's actually exactly the opposite; 99 is the easiest and 1 is the hardest easy level. I'm guessing that the e99 level is around 850 elo, and the e1 level is around 1600 elo.

You'll have to read through the README file to get familiar with the command-line switches, but it's not really that much work. On the line below are the command-line switches I use for the e1 level:
-s+ -b- -e1

(The -s+ switch "shows thinking on", the -b- switch "turns opening book off" (I use the GUI book instead), and the -e1 switch "turns easy level 1 on". Also note that easy levels set hashtable size to zero, pondering and learning to off.)

As a second example, on the line below are the command-line switches I use for the full strength level:
-s+ -t 131072 -b- -l-

(The -t 131072 switch sets the hash table size to 128 MB (131072 KB), and the -l- switch turns learning off.)


Now, for the stronger players, you might have noticed that there are no easy levels between e1 and full strength (about 1600 - 2400 elo). What to do? Are you just out of luck? Luckily, Dušan has added two new switches in this version: the -n switch and the -z switch. These two new switches let you specify the nodes/second and a bit of randomness into the evaluation function. So, by adding these two new command-line switches, you can create an engine strength between e1 and full strength.

I created nine new engine strengths in this rating gap. Assuming that I normally set the Phalanx full-strength hashtable to 128 MB, and the full-strength nodes-per-second reach about 600,000 to 650,000 nps (my PC isn't that powerful), here are the command-line switches for those nine engines (You can simply copy-and-paste the switches into your GUI during engine installation):

[Edit on Nov 9, 2014 - I've found that these settings for Easy 0.9 through Easy 0.1 are very nonlinear; I'm working on finding settings that are more linear, but it will take some time.]

Phalanx XXIII Easy 0.9 (about 1683 elo) :         -s+ -b- -l- -p- -n1000 -z 9 -t 256
Phalanx XXIII Easy 0.8 (about 1766 elo) :         -s+ -b- -l- -p- -n2000 -z 8 -t 512
Phalanx XXIII Easy 0.7 (about 1849 elo) :         -s+ -b- -l- -p- -n4000 -z 7 -t 1024
Phalanx XXIII Easy 0.6 (about 1932 elo) :         -s+ -b- -l- -p- -n8000 -z 6 -t 2048
Phalanx XXIII Easy 0.5 (about 2015 elo) :         -s+ -b- -l- -p- -n16000 -z 5 -t 4096
Phalanx XXIII Easy 0.4 (about 2098 elo) :         -s+ -b- -l- -p- -n32000 -z 4 -t 8192
Phalanx XXIII Easy 0.3 (about 2181 elo) :         -s+ -b- -l- -p- -n64000 -z 3 -t 16384
Phalanx XXIII Easy 0.2 (about 2264 elo) :         -s+ -b- -l- -p- -n128000 -z 2 -t 32768
Phalanx XXIII Easy 0.1 (about 2347 elo) :         -s+ -b- -l- -p- -n256000 -z 1 -t 65536

[Edit on Nov 9, 2014 - I've found that these settings for Easy 0.9 through Easy 0.1 are very nonlinear; I'm working on finding settings that are more linear, but it will take some time.]

(Note that the -p- switch sets pondering to off. Also, I don't know if the ratings for these nine settings are really linear, so the ratings are just a guesstimate.)


Here's the download link for the engine and the source code:
http://sourceforge.net/projects/phalanx/files/Version%20XXIII/

Here's some Chess Programming Wiki information on Phalanx and its creator:
http://chessprogramming.wikispaces.com/Phalanx
http://chessprogramming.wikispaces.com/Du%C5%A1an+Dobe%C5%A1

Here are some logos from Chess Mosaic:
http://www.chessmosaic.com/Phalanx1.html

And there's a really nice logo created by Jim Ablett inside this package (note that the engine in this package is a previous beta version):
http://kirr.homeunix.org/chess/engines/Jim%20Ablett/PHALANX/phalanx-xxiii-ja.zip

I hope you enjoy the engine!

_great_ article. thanks a lot.