Author: Keith Evans
Date: 11:42:12 04/10/03
Go up one level in this thread
On April 10, 2003 at 14:19:30, Robert Hyatt wrote: >On April 10, 2003 at 11:11:52, Vincent Diepeveen wrote: > >>On April 10, 2003 at 11:07:06, Robert Hyatt wrote: >> >>>On April 10, 2003 at 08:44:18, Vincent Diepeveen wrote: >>> >>>>On April 09, 2003 at 17:58:21, Robert Hyatt wrote: >>>> >>>>as usual you were asleep when replying. i did math for a single cpu. that >>>>extrapolates to more cpu's as well. >>> >>>I did math that extrapolates to _everything_. >>> >>>If I get 1.7X speedup for two cpus, I will get _some_ speedup no matter how slow >>>the >>>second processor is. >>> >>>Which was my point. >> >>with SMT that is not the case. the second cpu in SMT delivers somewhere between >>0% and 20%. >> >>If it is 10% like it is for most programs then: > > >Here is some _real_ data as opposed to your imaginary data. > >I took the last four positions you wanted me to run, which I assume you thought >were bad cases for Crafty. > >I ran them three times with SMT off, using mt=2. > >I then ran them three times with SMT on, using mt=4. > >Here are the results, giving the time for each of the positions, and the raw NPS >searched >for each position. > >-------smt=off-------- >---------mt=2--------- >time=57.12 nps=1617k >time=57.15 nps=1625k >time=1:00 nps=1617k >average=58.09 seconds > >time=32.02 nps=1807k >time=31.85 nps=1814k >time=32.32 nps=1805k >average=32.06 seconds > >time=1:00 nps=1468k >time=1:09 nps=1486k >time=1:06 nps=1481k >average=65 seconds > >time=51.68 nps=1711k >time=53.97 nps=1705k >time=54.73 nps=1699k >average=53.46 seconds > >-------smt=on--------- >---------mt=4--------- > >time=54.13 nps=1981k >time=56.10 nps=2041k >time=53.43 nps=2000k >average=54.5 seconds > >time=26.99 nps=2230k >time=25.71 nps=2303k >time=26.40 nps=2240k >average=26.37 seconds > >time=1:04 nps=1798k >time=1:00 nps=1835k >time=1:20 nps=1778k >average=68 seconds > >time=45.84 nps=2069k >time=44.76 nps=2135k >time=49.78 nps=2073k >average=46.79 seconds > >You can analyze the data any way you want. SMT on with mt=4 is faster for my >program >than SMT off with mt=2, contrary to your statements. Position three had one >run that was >slower by a significant margin than the others with SMT on. This is not that >uncommon. > >But overall, SMT is _clearly_ a win. Regardless of all that handwaving, >"proofing" and >whatever else it is you claim to be doing. > >Position 1runs 1.07X faster with SMT on. >Position 2 runs 1.22X faster with SMT on. >Position 3 runs .96X faster (slower) with SMT on. >Position 4 runs 1.14X faster with SMT on. > >If you do smoothing, to remove the oddball time from position 3 (remove the one >point >that took longer than any other by a significant margin) and you remove the >largest value >from the SMT=off case as well for balance, you get 63 secs average for SMT off, >and 62 >seconds average for SMT on, for a couple of percent improvement for SMT on. > >As I said, rather than flapping arms, and doing bogus math, it is _much_ easier >to simply >run the tests and look at the numbers. Something I always do, and something you >_never_ >seem to do. > >I wonder why that is??? Um... Because you always run them for him ;-) Do you really believe these positions were handpicked to make Crafty look bad? And if so then do you expect a larger performance increase for more typical positions? What machine were you running these on? I have a Dell PowerEdge 2650 with dual 2.8 GHz Xeons. (No I haven't run crafty on it yet, but would consider it if there were just a simple script to get those results.)
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