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. > > > > > > > > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
