mbootsector wrote:
Ok, then the results are more interesting.
Does the machine have two E5-2670 cpus? Intels pages show that E5-2670 has only 8 cores.
Exact! And is not a virtual server. It has Windows installed in the hard disk. Will be nice to know the results of someone with permanent access to one of these servers
YBWC and most other SMP schemes need a certain minimum depth before it catches on.
I can imagine that with very short time controls and very small depths a lazy SMP scheme has an advantage.
Not that anybody wants to play games with such short time controls in practice.
cdani wrote:
There are not a lot of games, but seems probable that with more time or with more threads lazy mp is better than stockfish standard.
That would surprise me. If I understood your post, your testing was done at very short time control---less than a minute for all moves.
I understand. I hope someone is able to do a longer test. I will try to do it also.
Here are the results of a 50 game match. Time control is 300+3. Each engine using 20 threads on a 20 core machine. Hash = 4 GB. Standard Stockfish testing book: 2moves_v1.pgn
It is a bit wasteful to determine effectivity of an SMP implementation (or in fact any speed-modifying change) by playing games. Measuring time-to-depth for a few hundred representative test positions should be enough to get a reliable impression. If the implementation would be 10% faster on average, it would very clearly stick out, and your accuracy could easily be good enough to distinguish 10% speedup from 9% speedup. 10% speedup would mean only 10 Elo improvement, i.e. about 1.5% score improvement, which would mean 3200 full games (~200,000 positions) to even convincingly (95% confidence) see there is an improvement. Now guess how many full games you need to see the difference between 9% and 10% improvement...
It is a bit wasteful to determine effectivity of an SMP implementation (or in fact any speed-modifying change) by playing games. Measuring time-to-depth for a few hundred representative test positions should be enough to get a reliable impression. If the implementation would be 10% faster on average, it would very clearly stick out, and your accuracy could easily be good enough to distinguish 10% speedup from 9% speedup. 10% speedup would mean only 10 Elo improvement, i.e. about 1.5% score improvement, which would mean 3200 full games (~200,000 positions) to even convincingly (95% confidence) see there is an improvement. Now guess how many full games you need to see the difference between 9% and 10% improvement...