Author: Robert Hyatt
Date: 19:39:39 04/13/03
Go up one level in this thread
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... > >Let's ignore the cpu=464% i do not understand why it says that. I have it at >mt=2. probably small i/o bug. > >Now let's diep search for around this time: > >Took 0.12 seconds to start all 1 other processes out of 2 >00:00 21 0k 0 0 21 (2) 2 (0,0) -0.022 Ng1-f3 d7-d5 >++ d2-d4 procnr=0 terug=1 org=[-22;-21] newwindow=[-22;520000] >00:00 71 0k 0 0 71 (2) 2 (0,0) 0.001 d2-d4 d7-d5 >00:00 175 0k 0 0 175 (2) 3 (0,2) 0.157 d2-d4 d7-d5 Ng1-f3 >00:00 443 0k 0 0 443 (2) 4 (0,5) 0.001 d2-d4 d7-d5 Ng1-f3 Ng8-f6 >00:00 150800 151k 0 0 1508 (2) 5 (0,19) 0.190 d2-d4 d7-d5 Ng1-f3 Ng8-f6 Nb1-c3 >00:00 318900 319k 0 0 3189 (2) 6 (0,27) 0.001 d2-d4 d7-d5 Ng1-f3 Ng8-f6 Nb1-c3 N >b8-c6 >00:00 149744 150k 0 0 13477 (2) 7 (3,68) 0.179 d2-d4 d7-d5 Ng1-f3 Ng8-f6 Bc1-f4 >Nf6-h5 Bf4-g5 >00:00 136110 136k 0 0 27222 (2) 8 (6,147) 0.001 d2-d4 d7-d5 Ng1-f3 Ng8-f6 Bc1-f4 > Nf6-h5 Bf4-g5 Nb8-c6 >00:01 127109 127k 0 0 205917 (2) 9 (45,502) 0.105 d2-d4 Ng8-f6 Nb1-c3 Nb8-c6 Bc1 >-f4 d7-d6 Ng1-f3 Bc8-f5 e2-e3 >00:04 127013 127k 0 0 572829 (2) 10 (76,666) 0.001 d2-d4 Ng8-f6 Nb1-c3 d7-d5 Bc1 >-f4 Bc8-f5 Ng1-f3 Nb8-c6 Nf3-e5 Nf6-e4 >00:17 152655 153k 0 0 2648566 (2) 11 (330,1980) 0.108 d2-d4 d7-d5 Ng1-f3 Nb8-c6 >Nb1-c3 Bc8-f5 Nf3-h4 Bf5-c8 Bc1-g5 Ng8-f6 e2-e3 >00:38 154041 154k 0 0 5889009 (2) 12 (743,4189) 0.008 d2-d4 d7-d5 Bc1-f4 Bc8-f5 >Ng1-f3 Ng8-f6 Nb1-c3 Nb8-c6 Nc3-b5 Ra8-c8 Nf3-e5 Nc6xe5 d4xe5 > >Of course if i use same conditions like crafty when to split then it will look >different with regards to the number of splits performed. > >Splitting in diep is very cheap. I already split >= 2 ply left searches and i >split quickly in current versions. I split everywhere. It is possible to limit this and I think the current version avoids splitting at the last 2-3 plies of the tree. I haven't tested this on my dual to see if the current value is correct, however... > The reason is that you get 500 cpu's quicker >busy and find bugs sooner. No doubt in future i will again optimize it to a >state where it will optimize search depth more at x86. If that's with many >splits a second at 2-4 processes, then i'll go for that. If it is with less >splits a second i'll go for that. > >Note that the 4189 number at 12 ply is not the number of splits only, it is the >total number of searches. So about 11*20 + 1 = 220 + 1 = 221 are from searching >the root. > >>On April 13, 2003 at 08:32:37, Vincent Diepeveen wrote: >> >>>On April 13, 2003 at 08:21:42, Vincent Diepeveen wrote: >>> >>>>On April 13, 2003 at 02:37:57, Tom Kerrigan wrote: >>>> >>>>>On April 13, 2003 at 01:04:52, Robert Hyatt wrote: >>>>> >>>>>>It _is_ pinned on SMT. The two logical processors are producing wildly >>>>>>imbalanced results when using threads, vs using two separate processes. It >>>>>>would appear to be cache-related... >>>>> >>>>>This is some sort of joke, right? You and Vincent see the same behavior, you >>>>>have SMT and Vincent doesn't, and somehow the problem is with SMT? >>>>> >>>>>How much of the time are your threads idle, out of curiosity? If one thread is >>>>>idle much more than the other, then of course that is going to skew your NPS. >>>>> >>>>>-Tom >>>> >>>>Of course both Crafty and DIEP are using YBW. I didn't checkout what bob does >>>>here, but in past in DIEP i used to always let process 0 let the search start. >>>>Nowadays that is not the case. The i/o thread picks the first process it can >>>>get. All search processes are completely identical. This process then is >>>>starting the search. That means the other CPUs idle when this process starts the >>>>search. >>> >>>also read that 'idle' not in litterary sense. Letting them REALLY idle with >>>sleep() or WaitForSingleObject, is at a REAL smp system (like dual K7) just too >>>expensive. Latency to wake up processors is at sick high levels. 15 ms just like >>>that. Imagine that because of the YBW search, you have to split initially like >>>50-100 times a second. 15ms is death sentence. So 'idle' cpu's are spinning >>>around until at a shared memory variable some flag is set. I let them do some >>>arithmetic function for a 100 times while 'idling'. >> >>If you do this right you won't split _that_ often. >> >> time=35.97 cpu=381% mat=-1 n=80006982 fh=92% nps=2224k >> ext-> chk=1487513 cap=353299 pp=32860 1rep=79236 mate=15135 >> predicted=3 nodes=80006982 evals=19493470 >> endgame tablebase-> probes done=0 successful=0 >> SMP-> split=1840 stop=163 data=15/64 cpu=2:17 elap=35.97 >> time used: 29.81 >> >> >>In the above from a game on ICC, in 35 seconds, I did 1800 splits total. The >>deeper the search the better this becomes... >> >> time=2:33 cpu=396% mat=0 n=282753699 fh=91% nps=1840k >> ext-> chk=3046093 cap=1083298 pp=16735 1rep=192964 mate=3400 >> predicted=8 nodes=282753699 evals=114936261 >> endgame tablebase-> probes done=0 successful=0 >> SMP-> split=2683 stop=424 data=15/64 cpu=10:09 elap=2:33 >> time used: 8.29 >> >> time=4:03 cpu=396% mat=0 n=466004128 fh=90% nps=1911k >> ext-> chk=3120074 cap=1773259 pp=60704 1rep=227466 mate=5595 >> predicted=9 nodes=466004128 evals=160300467 >> endgame tablebase-> probes done=0 successful=0 >> SMP-> split=5811 stop=950 data=18/64 cpu=16:06 elap=4:03 >> time used: 2:43 >> >> time=3:47 cpu=396% mat=0 n=421757405 fh=92% nps=1855k >> ext-> chk=3436512 cap=1222511 pp=75583 1rep=186606 mate=3165 >> predicted=12 nodes=421757405 evals=149496490 >> endgame tablebase-> probes done=0 successful=0 >> SMP-> split=3524 stop=337 data=17/64 cpu=15:01 elap=3:47 >> >>> >>>>In crafty that's also the case, but i do not know whether Bob always picks a >>>>certain thread as first. If so then that might explain quite something. >>>> >>>>Measuring idle time with SMT is very hard to do objective, but of course you can >>>>relatively check it out. Basically the problem is you do not know what the >>>>maximum % is that i can get out of SMT, because it is dependant upon the other >>>>process too.
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