bus error in Integer calculations

Geraint Jones Geraint.Jones at wolfson.ox.ac.uk
Thu Dec 8 23:43:08 UTC 2016

I have this little demo which I use for sixth formers which includes
calculating in fairly rapid order the sum of the digits of the
10^9th Fibonacci number.  (I haven't got enough physical memory to 
do the same for the 10^10th number without thrashing...)  It fell 
over on a flashy new macbook I was going to use for the presentation 
the other day; indeed I found I couldn't even calculate the sum of
the digits of the 10^6th number.  

I've reduced the problem to calculating numbers as large as 2^10000000
(as an Integer, of course), which works on all the ghci 7.8.4 
implementations I can find on various machines around the department, 
but which falls over on the 8.0.1 implementation on my macbook.

2^1000000 is fine, but 2^10000000 causes a bus error which may well
be a stack overflow in libHSinteger-gmp-

I don't seem to have easy access to 8.0.1 elsewhere or other
implementations on a mac.  Does anyone have a handle on whether this
is a problem with the sizing of the mac implementation or whether it
is a pervasive 8.0.1 problem?  Either way, it doesn't seem friendly 
that it manifests as an uncaught bus error.

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