Have Crafty's threads never gone to sleep?

[bob]

2 cores is something like 1.7x to 1.8x faster (for Crafty) averaged over a lot of positions. That is pretty significant in terms of additional speed.

I have been testing my program on a laptop with a Core 2 Duo CPU. I use two threads for computing. The program runs with a small set of 20 positions and stop when a solution for each is found.

I have tested several times and see that my smp version (of two threads) always loses on time to non-smp (1 thread) version. Looking at results, I see that event the last solutions are the same, the trees of smp and non-smp version are different, so in general smp one gets the ultimate solutions for more time compares with non-smp one event it has a higher nps.

Then I have searched, read some topic threads in this forum as well as your papper "The DTS high-performance parallel tree search algorithm" and see that your methodology of testing and test set are differs from my current one.

I roughly note some conclusions:

1) Smp is helpful for opening and middle periods, when for a given time, smp version can search deeper than single one. However, the replies (bestmoves) may be deferent because of diferent search trees

2) The endgame period is not clear who is the winner. The single thread may be faster than multi-threads ones.

Am I correct?
Many thanks in advance.

I do not see circumstances where single thread is better in endgame. yes, you might find a position here and there where that is true, but that is an exception. And those exceptions exist in opening and middlegame as well.

As far as your first conclusion goes, it is correct. Non-deterministic behaviour can produce different moves, different scores, different everything...