Luke Andrew wrote: > main = do print $ zipWith (+) (fiblist2 37 `par` fiblist1 37) > (fiblist2 37) > > compilation & testing: > > [EMAIL PROTECTED]:~/mcls$ ghc -O2 -threaded --make test2 > > [EMAIL PROTECTED]:~/mcls$ time ./test2 +RTS -N1 > [2,2,4,6,10,16,26,42... ...405774,18454930,29860704,48315634] > > real 0m15.294s > user 0m15.196s > sys 0m0.013s > > [EMAIL PROTECTED]:~/mcls$ time ./test2 +RTS -N2 > [2,2,4,6,10,16,26,42... ...405774,18454930,29860704,48315634] > > real 0m15.268s > user 0m15.169s > sys 0m0.013s
This is due to lazyness: 'fiblist2 37' does not evaluate the whole resulting list, so the thread spawned by 'par' will almost immediately return. Take a look at Control.Parallel.Strategies, the 'parList' combinator is probably what you need here. To get a feel what this 'strategies' stuff is all about, it is a good idea to read (or at least skim over) the accompanying paper, just google for "Algorithm + Strategy = Parallelism". Cheers Ben _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
