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Programming-Idioms

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  • Perl

Idiom #188 Matrix multiplication

Perform matrix multiplication of a real matrix a with nx rows and ny columns, a real matrix b with ny rows and nz columns and assign the value to a real matrix c with nx rows and nz columns.

use PDL::Basic qw(sequence);
use PDL::Primitive qw(matmult);
my ($nx, $ny, $nz) = (2, 3, 4);
my $A = sequence $ny, $nx;
my $B = sequence $nz, $ny;
my $C = matmult $A, $B;
(defn t [x] (apply (partial mapv vector) x))
(defn v* [u v] (reduce + (mapv * u v)))
(defn shape [a] (comp (partition-all (count a)) (map vec)))

(defn mm [a b]
    (into [] (shape a)
        (for [line a col (t b)]
            (v* line col))))

(def c (mm a b))

New implementation...