Matrix multiplication: Difference between revisions

=={{header|Go}}==

<lang go>package main

import (

"fmt"

)

type Value float64

type Matrix [][]Value

func Multiply(m1, m2 Matrix) (m3 Matrix, ok bool) {

rows, cols, extra := len(m1), len(m2[0]), len(m2)

if len(m1[0]) != extra { return nil, false }

m3 = make(Matrix, rows)

for i := 0; i < rows; i++ {

m3[i] = make([]Value,cols)

for j := 0; j < cols; j++ {

for k := 0; k < extra; k++ {

m3[i][j] += m1[i][k] * m2[k][j]

}

}

}

return m3, true

}

func (m Matrix) String() string {

rows := len(m)

cols := len(m[0])

out := "["

for r := 0; r < rows; r++ {

if r > 0 { out += ",\n " }

out += "[ "

for c := 0; c < cols; c++ {

if c > 0 { out += ", " }

out += fmt.Sprintf("%7.3f", m[r][c])

}

out += " ]"

}

out += "]"

return out

}

func main() {

A := Matrix{[]Value{1, 1, 1, 1},

[]Value{2, 4, 8, 16},

[]Value{3, 9, 27, 81},

[]Value{4, 16, 64, 256}}

B := Matrix{[]Value{ 4.0 , -3.0 , 4.0/3, -1.0/4 },

[]Value{-13.0/3, 19.0/4, -7.0/3, 11.0/24},

[]Value{ 3.0/2, -2.0 , 7.0/6, -1.0/4 },

[]Value{ -1.0/6, 1.0/4, -1.0/6, 1.0/24}}

P,ok := Multiply(A,B)

if !ok { panic("Invalid dimensions") }

fmt.Printf("Matrix A:\n%s\n\n", A)

fmt.Printf("Matrix B:\n%s\n\n", B)

fmt.Printf("Product of A and B:\n%s\n\n", P)

}</lang>

Output:

<pre>

Matrix A:

[[ 1.000, 1.000, 1.000, 1.000 ],

[ 2.000, 4.000, 8.000, 16.000 ],

[ 3.000, 9.000, 27.000, 81.000 ],

[ 4.000, 16.000, 64.000, 256.000 ]]

Matrix B:

[[ 4.000, -3.000, 1.333, -0.250 ],

[ -4.333, 4.750, -2.333, 0.458 ],

[ 1.500, -2.000, 1.167, -0.250 ],

[ -0.167, 0.250, -0.167, 0.042 ]]

Product of A and B:

[[ 1.000, 0.000, -0.000, -0.000 ],

[ 0.000, 1.000, -0.000, -0.000 ],

[ 0.000, 0.000, 1.000, -0.000 ],

[ 0.000, 0.000, 0.000, 1.000 ]]

</pre>