I missed that. I think this is an elegant way that avoids explicit rank. On Tue, Jul 19, 2022 at 2:13 PM Hauke Rehr <hauke.r...@uni-jena.de> wrote:
> Tom did, in the very post starting this thread: > > (1+i. 4 3) +/ . * 1+i. 3 4 > 38 44 50 56 > 83 98 113 128 > 128 152 176 200 > 173 206 239 272 > > Am 19.07.22 um 20:10 schrieb Devon McCormick: > > I'm puzzled why no one has used the basic matrix multiplication > expression > > in J. > > > > matmul3 > > ([: +/ *)"1 _ > > mat1=. <.0.5+10*<:+:1000 1000?@$0 > > mat0=. <.0.5+10*<:+:1000 1000?@$0 > > (10) 6!:2 'mat0 matmul3 mat1' > > 0.737084 > > (10) 6!:2 'mat0 +/ . * mat1' > > 0.0499271 > > (mat0 matmul3 mat1) -: mat0 +/ . * mat1 > > 1 > > > > > > > > On Tue, Jul 19, 2022 at 12:49 PM Thomas McGuire <tmcguir...@gmail.com> > > wrote: > > > >> My late night laziness and I got bitten by the 13 : definition doesn’t > >> always work > >> correctly with both x and y variables. Which I just assumed was working > >> correctly. > >> > >> Now when I fix the definition of matmul3 so it works correctly (as > Elijah > >> pointed out) the variable > >> representation does not incur a worrisome time penalty: > >> > >> (1+i. 4 3) ([: +/ *)"1 _ (1+i. 3 4) > >> 38 44 50 56 > >> 83 98 113 128 > >> 128 152 176 200 > >> 173 206 239 272 > >> matmul3 =: ([: +/ *)"1 _ > >> (1+i. 4 3) matmul3 (1+i. 3 4) > >> 38 44 50 56 > >> 83 98 113 128 > >> 128 152 176 200 > >> 173 206 239 272 > >> > >> 10 timex 'bmat1 ([: +/ *)"1 _ bmat2’ > >> 0.0464441 > >> 10 timex 'bmat1 matmul3 bmat2’ > >> 0.0471224 > >> > >> (bmat1 matmul3 bmat2) -: bmat1 ([: +/ *)"1 _ bmat2 > >> 1 > >> > >> > >> Thanks for showing me the error > >> > >>> On Jul 19, 2022, at 5:15 AM, Elijah Stone <elro...@elronnd.net> wrote: > >>> > >>> You are measuring two completely different things. > >>> > >>> 10 timex'bmat1 ([: +/ *)"1 _ bmat2' > >>> 0.0482293 > >>> 10 timex'bmat1 ([: +/ *"1 _) bmat2' > >>> 0.115583 > >>> (bmat1 ([: +/ *)"1 _ bmat2) -: (bmat1 ([: +/ *"1 _) bmat2) > >>> 0 > >>> ---------------------------------------------------------------------- > >>> For information about J forums see http://www.jsoftware.com/forums.htm > >> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > >> > > > > > > -- > ---------------------- > mail written using NEO > neo-layout.org > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA Quantitative Consultant ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
