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
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