Timing computation in cycles
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This page illustrates the use of the 'rdtsc' register on x86 machines to measure the number of cycles a chunk of Haskell code requires. We use lookup of a key in a map as an example.
The Rdtsc library is available from the libraries page.
import System.CPUTime.Rdtsc
import qualified Data.Map as M
import Text.Printf
import System.Environment
list =
["Baughn" ,"falconair" ,"Lemmih" ,"Philippa" ,"ToRA" ,"bd_" ,"felipe" ,"levitation[A"
,"Plareplane" ,"TSC" ,"bdash" ,"flux__" ,"lisppaste2" ,"Poeir" ,"tuukkah" ,"beelsebob"
,"fnordus" ,"lispy" ,"prb" ,"twanvl" ,"benc__" ,"fridim_" ,"liyang" ,"profmakx"
,"TwigEther" ,"benja_" ,"gaal" ,"LoganCapaldo" ,"Prozen" ,"uebayasi" ,"Betovsky"
,"gdsx" ,"lokadin" ,"psnl" ,"Ugarte" ,"bitshifter" ,"GeoBesh" ,"Lor" ,"pstickne" ,"ulfdoz"
,"bobwhoops" ,"george--" ,"loud-" ,"psykotic" ,"vegai" ,"bohanlon" ,"giksos" ,"lucca"
,"ptolomy" ,"vegaiW" ,"bos" ,"glguy" ,"Lunar^" ,"Pupeno" ,"Vq^" ,"bos31337" ,"gmh33"
,"Lunchy" ,"PupenoR" ,"waern" ,"Botje" ,"grumpy_old_one" ,"magagr" ,"pyronicide"
,"Wallbraker" ,"boulez" ,"GueNz" ,"mahogny" ,"quazaway" ,"wchogg" ,"cajole" ,"guillaumh"
,"makinen" ,"quetzal" ,"wilx`" ,"Cale" ,"gvdm_other" ,"MarcWeber" ,"qwr" ,"woggle"
,"calvins_" ,"Hirvinen" ,"maskd" ,"rafl" ,"wolverian" ,"cameron" ,"ibid" ,"mathrick"
,"ramkrsna" ,"xerox" ,"carp_" ,"Igloo" ,"mathrick_" ,"ramza3" ,"Xgc" ,"clanehin" ,"ikaros"
,"mattam" ,"rashakil_" ,"xian" ,"ClaudiusMaximus" ,"integral" ,"matthew-_" ,"ray"
,"xinming" ,"clog" ,"Jaak" ,"mauke" ,"rc-1" ,"xpika" ,"cmeme" ,"jbalint" ,"mbishop"
,"rds" ,"yaarg" ,"Codex_" ,"jcreigh" ,"metaperl" ,"reppie" ,"yosemite" ,"cods" ,"jdev"
,"Mitar" ,"resiak" ,"Z4rd0Z" ,"cognominal" ,"jgrimes" ,"mlh" ,"retybok" ,"zamez" ,"cpfr"
,"JKnecht" ,"moconnor" ,"rey_" ,"zeuxis" ,"ctkrohn" ,"jlouis" ,"monochrom" ,"saccade"
,"ziggurat" ,"daniel_larsson" ,"jmg_" ,"moonlite" ,"Saizan" ,"|shad0w|" ,"dany2k" ,"jmob"
,"mornfall" ,"SamB" ,"Daveman" ,"joene_" ,"mr_ank" ,"SamB_XP" ,"dblog" ,"johs_" ,"ms_"
,"scw" ,"dcoutts" ,"jrockway" ,"Muad_Dib" ,"shapr" ]
main = do
[v] <- getArgs
-- force evaluation (don't want to time evaluation of lazy structures)
length list `seq` return ()
let m = M.fromList (zip list [1..])
M.size m `seq` return ()
-- do the lookup
t <- rdtsc
k <- M.lookup v m
u <- rdtsc
print k
printf "%d cycles\n" (fromIntegral (u - t) :: Int)
Running this:
$ ./A shapr 161 3058 cycles