Hi David,


On Tue, Jan 1, 2013 at 12:24 PM, David T. Lewis <lewis at mail.msen.com> wrote:

> On Tue, Jan 01, 2013 at 03:47:54PM +0000, commits at source.squeak.org wrote:
> > Nicolas Cellier uploaded a new version of Kernel to project The Trunk:
> > http://source.squeak.org/trunk/Kernel-nice.725.mcz
> >
> > ==================== Summary ====================
> >
> > Name: Kernel-nice.725
> > Author: nice
> > Time: 1 January 2013, 4:47:30.911 pm
> > UUID: 52a4994f-63bc-4f71-9f8f-6f2fad460bde
> > Ancestors: Kernel-nice.724
> >
> > Fast-up large integer modulo operations (\\ and rem:)
> >
> > Implementation notes:
> > Quotient and remainder are computed in a single LargeIntegersPlugin
> primitive (see digitDiv:neg:) so it's faster to just use it.
> > For LargeInteger with 64 bits or less, LargeInteger primitives (31 32
> 33) are faster than the plugin (especially in COG) so try them first.
> > This results in a 2x speed up of modulo operations in 4.2.5 VM (whatever
> bit length), and a 2x speed up in COG VM for bit length > 64.
> > There is a penalty of 15% in COG for #rem: when bit length <= 64 because
> there is no primitiveRem...
> > Well, I added primitiveRem and it is in both VM branches, but it has no
> primitive number assigned.
> > If we assign a primitive number (20 ?) we can expect a 5x speed up for
> rem and bitLength <= 64.
>
> Should we assign primitive number 20 to primitiveRemLargeIntegers? It is in
> the range of numbered primitives allocated for large integer prims, and is
> currently unused in both the interpreter VM and Cog.
>
> I can't think of any reason not to do this, so someone please speak up if
> it might cause problems.
>
> Eliot, is this ok for Cog and Newspeak etc?
>

Fine by me.  20 isn't even used in Smalltalk-80 V2, and isn't by
VisualWorks.  Seems ideal.
-- 
best,
Eliot
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