The implementation is floating point.

Henry Rich

On Mon, Jan 9, 2023, 8:24 PM Marshall Lochbaum <mwlochb...@gmail.com> wrote:

> The matrices in my example are integral.
>
> Marshall
>
> On Mon, Jan 09, 2023 at 05:20:49PM -0800, Elijah Stone wrote:
> > I've thought in the past that it would be nice to have a mode for
> > reproducible fp, but there is none yet (try +/ vs ([+])/).  But it is
> moot
> > in this case, as the matrices in question were integral.
> >
> > (I don't think strict interpretation per se is necessary; just something
> > reliable and consistent.  EG I imagine picking and committing to a way of
> > associating +/ which requires log space but admits efficient
> implementation
> > on any sort of parallel architecture.)
> >
> > On Mon, 9 Jan 2023, Marshall Lochbaum wrote:
> >
> > > I don't think you'd want to reorder matrix multiplications as that can
> > > change the results by an arbitrary amount. Here's an example where
> > > multiplication on one side cancels but not on the other side.
> > >
> > >   (+/ .*&.>/ , +/ .*&.>~/@:|.) 1e6 1e7;(1e13+=i.2);1 _1
> > > ┌────────┬──────────┐
> > > │_9000000│_8.99482e6│
> > > └────────┴──────────┘
> > >
> > > Marshall
> > >
> > > On Mon, Jan 09, 2023 at 01:45:32PM -0500, Henry Rich wrote:
> > > > If f is known to be associative, f/\ proceeds from start to end in
> linear
> > > > time.  Elijah has thoughts about how you could inform the
> interpreter that a
> > > > function is associative. Till that is implemented, you can use
> f/\.&.|.
> > > > which has linear time, or you can use Fold.
> > > >
> > > > Henry Rich
> > > >
> > > > On 1/9/2023 1:23 PM, Omar Antolín Camarena wrote:
> > > > > Am I right in thinking that the J interpreter does use a linear
> time algorithm for u/\ for some u including + and *? If so, maybe the case
> of +/ . * is worth adding.
> > > > >
> > > >
> > > >
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