schedule: invalid what_next field

internal error: schedule: invalid what_next field

I'm studying a program which runs without trouble within ghci but fails to run well once compiled with ghc --make.

• The program
• The error message
• The ways I get or not the error message

The program ==

It is a computing of the index for which the length of the longuest sequence during a Syracuse process [(/2) if even u, (+1).(*3) if odd u] is reached.

boundary variable is the only parameter.

For instance, the program returns 3 for

boundary=5

because [x <- [2..n](BR]] the 1-process [1->] has 0 element, [[BR]] the 2-process [2->1] has 1 element, [[BR]] the 3-process [3->10,5,16,8,4,2,1] has 7 elements, [[BR]] the 4-process [4->2,1] has 2 elements and [[BR]] the 5-process [5->16,8,4,2,1] has 5 elements [[BR]] so the index for which the maximum is reached is '''3''' (for a length maximum of 7).

{{{ -- syracuse.hs import Data.Array import Data.Ord

boundary=25999

maximumBy g x = fst $ (foldr (maxBy g) (0,0) x)

maxBy comp x y=case (comp x y) of GT -> x EQ -> y LT -> y

syrs n = a where a = listArray (1,n) $ 0:[ syr x )

syr x = if x' <= n then 1 + a ! x' else 1 + syr x'

where x' = if even x then x div 2 else 3 * x + 1

main = print $ maximumBy (comparing snd)$ assocs $ syrs boundary

}}}

The error message

syracuse.exe: internal error: schedule: invalid what_next field [[BR]]

(GHC version 6.10.1 for i386_unknown_mingw32)[[BR]]

Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug [[BR]]

This application has requested the Runtime to terminate it in an unusual way. [[BR]] Please contact the application's support team for more information. [[BR]]

The ways I get or not the error message

I'm running Windows XP SP3 on a ~1GHz CPU/ ~1Go RAM computer.[[BR]] Within ghci, I'm only limited by memory (I get an *** Exception : stack overflow for boundary=140000) and I can compute up to

boundary=130000

for which the program returns 106239.

On the other hand, when I compile using

ghc --make syracuse

everything 's all right up to boundary=25998 (result:23529, Exit code: 0 ) but as far as boundary>25998, the program displays the result (for instance I can get 106239 again) but the error message is also displayed with Exit code: 3.

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
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