? about lazy SMP

[Chessnut1071]

[d] 1n3r2/3k2pp/pp1P4/1p4b1/1q3B2/5Q2/PPP2PP1/R4RK1 w - - 0 1

Without lazy SMP my engine finds the solution in under 7 seconds, looking at 11.502,081 nodes; 9,936,168 white and 1,565,913 black. If so, can anybody find the solution to the FEN above examining less nodes than the 11,502,801 above with a better implementation of lazy SMP? Since my engine is slow, nodes is a better comparison than time.

With only one core, Myrddin finds Mate in 7 at depth 7 in 0.06 seconds after searching only 76,414 nodes. Myrddin's Lazy SMP implementation just launches extra processes with slightly different search depth parameters so that the primary process can find the best move more quickly, but searching MANY more nodes, of which an embarrassingly large percentage are redundant but hopefully found in the hash table.

So in this case, with 4 cores, Myrddin finds Mate in 7 at depth 7 in 0.04 seconds (about 2/3 the time), but after searching 156,279 seconds (more than 2x nodes).

Any info on what Myrddin was running on, language it used, and what algorithm it used to achieve those results? I notice that even with 4 cores there's not much improvement because of the redundancy.

never mind, just found it, very impressive piece of work. thx

[JVMerlino]

Any info on what Myrddin was running on, language it used, and what algorithm it used to achieve those results? I notice that even with 4 cores there's not much improvement because of the redundancy.
never mind, just found it, very impressive piece of work. thx

Well, thank you for saying so, but I just kind of hacked it in as a quick and dirty solution that I hoped would work.

But when the solution for a position is found very quickly, as in the one you posted, you won't see much improvement from multiple cores in any case. But, for example, in this position:

[d]5r2/pb3p1k/1pn3p1/2p1PP2/8/b2RQ3/qP4PP/5R1K w - - bm Qh3 -- Mate in 9

...with one core Myrddin needs 16.8 seconds to get to the first fail high on Qh3, and 88.2 seconds to resolve it to the Mate in 9. But with 8 cores the first fail high comes in 1.6 seconds, and Mate in 9 is announced in 16.4 seconds.

But keep in mind that Myrddin's SMP implementation is non-deterministic, so different runs can exhibit widely different results in test positions. But this variance is "spread out" during full games, so that CCRL shows +76 elo for four cores, which I'm more than happy with.