Author: Robert Hyatt
Date: 21:07:21 04/15/03
Go up one level in this thread
On April 15, 2003 at 04:54:11, Tony Werten wrote: >On April 14, 2003 at 17:43:12, Robert Hyatt wrote: > >>On April 14, 2003 at 17:15:41, Vincent Diepeveen wrote: >> >>>On April 13, 2003 at 22:39:39, Robert Hyatt wrote: >>> >>>>On April 13, 2003 at 11:49:28, Vincent Diepeveen wrote: >>>> >>>>>On April 13, 2003 at 11:27:53, Robert Hyatt wrote: >>>>> >>>>>I said initially. It drops back to 10 splits a second in DIEP after a while. >>>>>Search depth matters. >>>>> >>>>>Let's compare 2 things. >>>>> >>>>> time=45.98 cpu=464% mat=0 n=37870294 fh=88% nps=823k >>>>> ext-> chk=638414 cap=249442 pp=9588 1rep=32966 mate=223 >>>>> predicted=0 nodes=37870294 evals=14565859 >>>>> endgame tablebase-> probes done=0 successful=0 >>>>> hashing-> trans/ref=28% pawn=93% used=28% >>>>> SMP-> split=431 stop=57 data=6/64 cpu=3:33 elap=45.98 >>>>> >>>>>MT 2 crafty 18.10 which i have here. 431 splits at 45 seconds. I guess you must >>>>>limit in crafty the number of splits a lot as splitting is expensive in crafty >>>>>when compared to the costs of a single node. >>>> >>>>I'm not sure how expensive it is compared to a node. I'll run a test where >>>>I do the split overhead at every node to compare, however... >>>> >>>> >>>> >>>>I don't limit them at all. The only limit is the YBW algorithm. But I split >>>>at the root also, which reduces them signficantly... >>> >>>I can split at the root nowadays, but i have turned it off for diep. it gives >>>too poor speedup for me. The interesting thing which searching SMP can give is >>>transpositions at a big depth which possibly are overwritten by a sequential >>>search. i don't want to miss them. >> >>Maybe you don't split at the root correctly. I limit this with some intelligent >>guesswork, so that if it appears that I might change my mind this iteration, >>then >>I don't split at the root until I have searched all moves that I think might >>replace >>the best move... > >Just trying to understand. Are you talking about the case where the best move in >the root got a fail low ? No. I search the first move with all processors for obvious reasons. I search the next "N" the same way, where "N" is set by trying to figure out how many moves _might_ become a new best move (I discover this by looking at the node counts for each move after an iteration ends. If any are close to (or bigger than) the node count for the first move, then they deserve special parallel searching one at a time, before I split at the root and search a root move with only one processor (which will take longer). > >When that happens, your testresults indicate that's it's better to split lower >than to search 2 rootmoves parallel in order to get an established score asap ? >( So not breaking off seacrh when 1 gets a first failhigh, but only when the >score is resolved ) > >Tony > >> >> >>>
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