Hi Jon,
You're more likely to get a useful response over on the
glasgow-haskell-users mailing list, as it looks like this is a GHC
specific bug: http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Running this at -N6 doesn't want to complete for me, so I'm not sure
if it would segfault. I'm on a 64-bit Intel Mac OS X using GHC 6.12,
dual core.
With such a small example as this your best bet would be to file a bug report:
http://hackage.haskell.org/trac/ghc/
You'll need to use the login guest/guest to file a new ticket.
Antoine
On Wed, Dec 23, 2009 at 9:14 PM, Jon Harrop
I took the parallel merge sort described here:
http://martin.sulzmann.googlepages.com/AMP-Spring2008-intro.pdf
and added a simple test:
main :: IO () main = do putStrLn $ show $ sum $ mergesort $ [sin x | x <- [1.0 .. 1000000.0]]
Compiled it with GHC 6.8.2 from Debian testing and ran it with various +RTS -N<n> arguments to measure its performance and obtained the following results on an 8 core:
$ ghc --make -O2 -threaded mergesort.hs -o mergesort [1 of 1] Compiling Main ( mergesort.hs, mergesort.o ) Linking mergesort ... $ time ./mergesort +RTS -N1 -0.117109518058233
real 0m9.723s user 0m9.461s sys 0m0.232s $ time ./mergesort +RTS -N2 -0.117109518058233
real 0m13.574s user 0m15.225s sys 0m0.140s $ time ./mergesort +RTS -N3 -0.117109518058233
real 0m13.185s user 0m15.529s sys 0m0.184s $ time ./mergesort +RTS -N4 -0.117109518058233
real 0m13.251s user 0m15.829s sys 0m0.336s $ time ./mergesort +RTS -N5 -0.117109518058233
real 0m13.093s user 0m16.929s sys 0m0.164s $ time ./mergesort +RTS -N6 Segmentation fault
real 0m5.711s user 0m7.408s sys 0m0.136s
That segfault must be due to a bug in GHC so I thought perhaps a newer version of GHC might fix the segfault but I installed GHC 6.10.4 from Sid and now I get:
$ ghc --make -O2 -threaded mergesort.hs -o mergesort Binary: Int64 truncated to fit in 32 bit Int ghc: panic! (the 'impossible' happened) (GHC version 6.10.4 for i386-unknown-linux): Prelude.chr: bad argument
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
I'll try the haskell-platform package next. Are these known problems?
-- Dr Jon Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/?e _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners