internal error: evacuate: strange closure type 32768

[Greg Buchholz]

    I'm running GHC v6.4 under Linux (2.6.3) and while trying to port the
spectralnorm benchmark of the Great Computer Language Shootout...

http://shootout.alioth.debian.org/benchmark.php?test=spectralnorm

...I encounter a strange failure mode when turning on optimizations.
For the code below enabling either the -O or -O2 level of optimization
results in the following error...

spectral_norm: internal error: evacuate: strange closure type 32768
    Please report this as a bug to glasgow-haskell-bugs at haskell.org,
    or http://www.sourceforge.net/projects/ghc/

...using a small value of "n" (say 20 instead of 1999) the unoptimized
version appears to work correctly, while the optimized versions report a
<<loop>>.


Thanks,

Greg Buchholz

-- Spectral Norm benchmark

import Array
import System(getArgs)

main = do
        --[arg] <- getArgs
        --let n = (read arg) - 1 
        let n = 1999
        let init = listArray (0,n) (repeat 1.0)
        let (v:u:rest) = drop 19 $ iterate (eval_AtA_times_u n) init
        let vBv = sum [(u!i)*(v!i) |i<-[0..n]]
        let vv  = sum [(v!i)*(v!i) |i<-[0..n]]
        print $ sqrt (vBv/vv)

eval_AtA_times_u n u = eval_At_times_u n v
    where v = eval_A_times_u n u

eval_A x y = 1.0/((i+j)*(i+j+1)/2+i+1)
    where i = fromIntegral x
          j = fromIntegral y

eval_A_times_u n u = accumArray (+) 0 (0,n)
                     [(i,(eval_A i j) * u!j)|i<-[0..n], j<-[0..n]]

eval_At_times_u n u = accumArray (+) 0 (0,n)
                      [(i,(eval_A j i) * u!j)|i<-[0..n], j<-[0..n]]