Got it - thanks. Any idea about the run-away process problem? Thanks, Warren
On Fri, Oct 15, 2010 at 9:32 AM, Daniel Fischer <[email protected]>wrote: > On Friday 15 October 2010 14:59:18, Warren Harris wrote: > > I trying to learn a bit about data parallel haskell, and started from > > the wiki page here: > > http://www.haskell.org/haskellwiki/GHC/Data_Parallel_Haskell. Two > > questions: > > > > The examples express the dot product as: > > > > dotp_double xs ys = sumP [:x * > > <http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:. > >> y | x <- xs | y <- ys:] > > > > Unless I'm missing something, shouldn't this actually be: > > > > dotp_double xs ys = sumP [:x * > > <http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v:. > >> y | x <- xs, y <- ys:] > > > > No, it's supposed to be a parallel list comprehension, the dot product is > > sum $ zipWith (*) xs ys > > and the > > { blah x y | x <- xs | y <- ys } > > syntax (where {, } stand in for [, ] in parallel list comprehensions and > for [:, :] in parallel array comprehensions) means > > { blah x y | (x,y) <- zip xs ys } > > > Second, when I run Main with the prescribed 10000 element array, > > everything seems to work quite nicely. The task takes about 2 seconds on > > my 4 processor x86_64, and threadscope shows all processors nicely > > utilized. However, when bumping this to 100000 elements, rather than > > taking 10x longer as I expected, the process never terminates. During > > one run I even lost control of my machine and needed to do a hard reset. > > Are there known limits to the array sizes that can be handled with dph, > > or can someone suggest what might be going wrong here? Thanks, > > > > Warren > >
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