2011/5/26 michael rice
Thank, Daniel
Multiple threads are in evidence in my system monitor, but I wonder why I'm getting two different answers, one twice the other. The first is the parallel solution and the second is the non.
Why do you add n1+n2+1 in the parallel program, but only n1+n2 in the non-parallel one ?
Michael
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{- import Control.Parallel
nfib :: Int -> Int nfib n | n <= 1 = 1 | otherwise = par n1 (pseq n2 (n1 + n2 + 1)) where n1 = nfib (n-1) n2 = nfib (n-2) -}
nfib :: Int -> Int nfib n | n <= 1 = 1 | otherwise = nfib (n-1) + nfib (n-2)
main = do putStrLn $ show $ nfib 39
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[michael@hostname ~]$ ghc --make -threaded nfib.hs [1 of 1] Compiling Main ( nfib.hs, nfib.o ) Linking nfib ... [michael@hostname ~]$ ./nfib +RTS -N3 204668309 [michael@hostname ~]$ ghc --make nfib.hs [1 of 1] Compiling Main ( nfib.hs, nfib.o ) Linking nfib ... [michael@hostname ~]$ ./nfib 102334155 [michael@hostname ~]$