Why do we put GMP allocations on GHC heaps?
fw at deneb.enyo.de
Mon Nov 4 20:36:20 UTC 2013
* Simon Marlow:
> We did originally look at targetting the mpn API, but decided against
> it for the reasons alluded to above - the mpz layer has quite a lot of
> stuff in it that you would need to replicate. For instance, when you
> start doing an operation some calculation has to be done to figure out
> how much memory to allocate for the result.
Sure, and you have to do sign handling. The advantage is that you
could use a convenient encoding for length and sign, or deal with
carry/borrow in a flexible manner (i.e., stealing another word from
the allocation buffer). It's not exactly trivial, but the effort may
be worth it.
> And be extra careful, because the GMP code is GPL, so our
> replacement for the mpz bits would probably end up being GPL too.
Actually, it's LGPL, and interesting bits are part of libc under an
even more permissive license.
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