Re: [Haskell-cafe] Parallel compilation and execution?

On 26/05/2011 14:32, michael rice wrote:

Fair question. I copied the parallel version from:

http://www.haskell.org/ghc/docs/6.6/html/users_guide/lang-parallel.html http://www.haskell.org/ghc/docs/6.6/html/users_guide/lang-parallel.html

That is the User Guide for GHC 6.6, incidentally. If you're using a later version of GHC (highly recommended especially for parallel stuff), then you should look at the docs for your version. Cheers, Simon

http://www.haskell.org/ghc/docs/6.6/html/users_guide/lang-parallel.htmlbut pulled the non-parallel version from a text.

Michael

--- On *Thu, 5/26/11, David Virebayre //* wrote:

From: David Virebayre Subject: Re: [Haskell-cafe] Parallel compilation and execution? To: "michael rice" Cc: haskell-cafe@haskell.org, "Daniel Fischer" Date: Thursday, May 26, 2011, 8:56 AM

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

===========

{- 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

=============

[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 ~]$

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