YBW engines past and present?

[Dann Corbit]

Did you try LazySMP?
Easy as falling off of a log and seems to work really well.

It's insane that seemingly small tweaks to what was considered the worst-scaling algorithm (shared hash table) somehow produces the best one.

I agree. In fact, it is kind of disturbing.

[syzygy]

Did you try LazySMP?
Easy as falling off of a log and seems to work really well.

It's insane that seemingly small tweaks to what was considered the worst-scaling algorithm (shared hash table) somehow produces the best one.

I don't think the small tweaks made the difference. In the old days testing an SMP implementation meant searching about 24 positions to a depth of about 8 and comparing total nodes, so I'm not sure there was any serious data to begin with. What may also have helped the shared hash table approach is the very low branching factor of modern engines.

[Daniel Shawul]

ABDADA was comparable to YBW even in the old days too, just wasn't given as much attention.
From what I recall, the author was bad-mouthed when the paper came out claiming a YBW algorithm
done all through the hashtable. Lazy SMP is certainly lazier but it is not better than ABDADA which is
still the best algorithm for Scorpio.

[Michel]

It's insane that seemingly small tweaks to what was considered the worst-scaling algorithm (shared hash table) somehow produces the best one.

It was never "worst scaling". In fact the old Toga used an extremely simple implementation of shared hash and its scaling was comparable to YBW engines. One can check this at CCRL. I pointed this out a few times but it was ignored.

The "tweaks" make little difference. In fact I think Stockfish has dropped all of them by now.

[Patrice Duhamel]

Cheese still use YBW, based on Stockfish implementation, but I will look at Lazy SMP and maybe ABDADA.

[Volker Annuss]

My engine Hermann was LazySMP. Although rating lists indicated, that Hermann with 4 cores was much stronger than with a single core, I was not satisfied with the speedup in time to depth with 4 ore more cores. So I started Arminius with a simple search and eval to have something clean to implement YBWC. Arminius has improved since then and is no longer that simple.

The latest public version of Arminius is a little more than 2 years old. It still uses YBWC. You can find it here:
http://www.nnuss.de/Hermann/Arminius2018-12-23.zip
http://www.nnuss.de/Hermann/Arminius201 ... nux.tar.gz
http://www.nnuss.de/Hermann/Arminius201 ... spi.tar,gz

Now I am on the way back to LazySMP. My latest development version has a UCI option to switch between LazySMP and YBWC, but it is not yet ready for release.