Some chess ramblings

-
I am spending some free time rewriting the first generation of my UCI chess engine BikJump into the second generation by replacing the "mailbox" representation with a home-brewed bitboard representation, while carefully revisiting all other parts of the engine as well. The switch to bitboards has improved search speed substantially. In a typical middle game position, the nodes-per-second rating of the search increased from around 500Kns to close to 2000Kns on a Intel Core 2 Quad Q6700 2.66GHz (single-threaded 64-bit binary).

Interesting enough, the strength increase is still disappointing given the major rewrite. Therefore, I am now performing experiments with tournaments and test positions to find more opportunities to enhance its strength.

I like this test position (white to move wins), which I found on TalkChess, one of my favorite forums on chess (thanks to Chess Imager for generating the diagram).





This is an anti "null move" position. The old BikJump, which tries a null move after full move generation only when sufficient moves are possible, found the forced mate very quickly. The new BikJump performs the null move prior to full move generation to enhance searching speed. As a result, however, the mate is no longer found in reasonable time (just like many strong chess engines fail to find it quickly). Common wisdom is that the second approach is better, since the position above is unlikely to occur in real games. It leaves me somewhat weary though. Would a strong human chess player find the mate quickly? And if so, do current chess engines, which beat the strongest players but struggle on positions like this, truly pass the Turing test? Opinions?

Comments

Unknown said…
Perhaps you can change your search to recognize the conditions that render this zugzwang and avoid the null move in this case.
November 12, 2008 at 12:43 PM
Aart Bik said…
You hit the nail on the head, and better chess engines do just that. However, in BikJump I have not found such a recognition method that is considerably cheaper than move generation (also see the Oct 24 posting).
November 12, 2008 at 4:49 PM
Post a Comment

Popular posts from this blog

Checkers Move Generation

-
I was able to make a small improvement in the checkers move generator (written in Java for the Android SDK). The following table shows run times of several perft depths before and after optimization when run on the emulator (which should mimic actual run times on the phone quite well). DEPTH #LEAF NODES ORIGINAL OPTIMIZED TIME TIME ==================================== 7 179740 2.9s 1.9s 8 845931 14.2s 9.7s 9 3963680 66.3s 45.6s 10 18391564 294.6s 208.7s P.S. Runtimes for a C++ checkers move generator on a 2.2 GHz Core 2 Duo are given at my checkers page .
Read more

Connecting Chess for Android to a Remote Server

-
Image
I have received several questions on how to connect Chess for Android running on an Android device (e.g. a phone) as client to a remote chess server (e.g. a powerful desktop), so I decided to write a small document with detailed instructions. What you will need: The server software from Bernhard Wallner's chess utilities , suited for your server's operating system (if, say, your desktop runs Windows, you will need to download the Windows version). You do not need to download the client software in this case. The network enabled version of Chess for Android . On the server, start the engine server software, and construct a new row for every engine you want to run remotely. Assign a name, port number, and select the full path to each engine binary (an executable that runs on the server). You can also supply command line options for starting the engine. Check the active checkboxes and click start when done. This yields something similar to the screenshots below. Here, I have s...
Read more

Connecting with the DGT Board

-
Image
After all the fun I had connecting Chess for Android with the Millennium  over Bluetooth, I was curious if I could provide similar support for the DGT electronic chess boards. Some of these have Bluetooth capabilities, most use USB connections, and some older models, like the one I have, still use the RS-232 connector. To my pleasant surprise, by combining the original serial cable of DGT with a USB-to-serial cable and a female-USB-to-USB-C cable, I was able to get an actually working connection between my DGT board and my tablet or phone. Next was implementing support in Chess for Android. Luckily, DGT kindly shared the protocol documentation with me, and after a fun weekend of hacking, Chess for Android now proudly supports DGT electronic chess boards as well.
Read more