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# 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))```
`(require '[clojure.core.matrix :refer [mmul]])`
`(def c (mmul a b))`
`c = matmul (a,b)`
`import "gonum.org/v1/gonum/mat"`
```c := new(mat.Dense)
c.Mul(a, b)```
`uses typ, omv;`
```var
A: array[1..m, 1..n] of ArbFloat;
B: array[1..n, 1..p] of ArbFloat;
C: array[1..m, 1..p] of ArbFloat;

...

omvmmm(
A[1,1], m, n, n,
B[1,1], p, p,
C[1,1], p
);```
`import numpy as np`
```c = a @ b
```
`import numpy as np`
`c = np.matmul(a, b)`
`require 'matrix'`
`c = a * b`

tkoenig