On Wed, Jul 7, 2010 at 11:36 PM, Jason Moxham <ja...@njkfrudils.plus.com>wrote:

> On Tuesday 06 July 2010 10:49:35 Bill Hart wrote:
> > Frederick is working on mpz_mulhi, however one thing we *really* need
> > (since the interesting case for his applications is for a small number
> > of limbs) is an x86_64 assembly version for the basecase, as at
> > present I think we just use a full multiplication. I think this should
> > save a large percentage of the time (nearly half I think).
> >
> > Jason, do you by any chance have any code for this?
> >
>
> I can easily write one , which one do we want though
> ie size n * size n to top n digits or the general xn* yn to zn or some
> inbetween one?
>

Hi Jason, that would be awesome.

The general case is probably necessary. More specifically, the application
is to multiply fixed-point numbers x, y, which don't have to be the same
size, discarding a fixed number of the lower limbs (i.e.computing an
approximation of floor(x*y / 2^(n*GMP_LIMB_BITS)) for integers x and y of
arbitrary length).

Fredrik

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