[nhc-users] fps and Foreign(Obj/Ptr)

[Don Stewart]

Malcolm.Wallace:
> "Donn Cave" <donn at avvanta.com> wrote:
> 
> > I've run into a problem where it looks like my application crashes
> > with "Error: allocation limit (1024) exceeded for Foreign(Obj/Ptr)"
> > because it's using too many ByteStrings.  Does that seem plausible?
> 
> Yes, it seems plausible.  nhc98's runtime system has a constant-size
> table for storing ForeignPtrs.
> 
> > Can I simply increase the size of that foreign[] array, by several
> > orders of magnitude, to get around this?
> 
> Yes, but you will need to recompile nhc98's RTS.  (Not hard.) In
> src/runtime/Kernel/cdata.c, just change the #define'd constant
> MAX_FOREIGNOBJ, and then (at the toplevel)
>     make runtime
>     make install
> 
> *However*, you should also be aware that ByteStrings have been optimised
> for use in ghc, not nhc98.  In fact, it turns out that using ByteString
> is orders of magnitude slower than using plain String, in nhc98.  I
> can't remember the exact factor, but it was something of the order of
> 60x slower.

For one benchmark.

I'd imagine there's others where space is a premium, where it would be
no contest to use a packed representation.

-- Don