> I've enjoyed reading Simon Marlow's new tutorial on parallel and concurrent programming
I am interested: where I this tutorial? 2011/6/3 John D. Ramsdell <ramsde...@gmail.com> > I've enjoyed reading Simon Marlow's new tutorial on parallel and > concurrent programming, and learned some surprisingly basic tricks. I > didn't know about the '-s' runtime option for printing statistics. I > decided to compute speedups for a program I wrote just as Simon did, > after running the program on an unloaded machine with four processors. > When I did, I found the speedup on two processors was 2.4, on three > it was 3.2, and on four it was 4.4! Am I living in a dream world? > > I ran the test nine more times, and here is a table of the speedups. > > 2.35975 3.42595 4.39351 > 1.57458 2.18623 2.94045 > 1.83232 2.77858 3.41629 > 1.58011 2.37084 2.94913 > 2.36678 3.63694 4.42066 > 1.58199 2.29053 2.95165 > 1.57656 2.34844 2.94683 > 1.58143 2.3242 2.95098 > 2.36703 3.36802 4.41918 > 1.58341 2.30123 2.93933 > > That last line looks pretty reasonable to me, and is what I expected. > Let's look at a table of the elapse times. > > 415.67 176.15 121.33 94.61 > 277.52 176.25 126.94 94.38 > 321.37 175.39 115.66 94.07 > 277.72 175.76 117.14 94.17 > 415.63 175.61 114.28 94.02 > 277.75 175.57 121.26 94.10 > 277.68 176.13 118.24 94.23 > 277.51 175.48 119.40 94.04 > 415.58 175.57 123.39 94.04 > 277.62 175.33 120.64 94.45 > > Notice that the elapse times for two and four processors is pretty > consistent, and the one for three processors is a little inconsistent, > but the times for the single processor case are all over the map. Can > anyone explain all this variance? > > I have enclosed the raw output from the runs and the script that was > run ten times to produce the output. > > John > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >
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