gglm/gglm/mat2.go

package gglm

import (
	"fmt"

	"gonum.org/v1/gonum/blas/blas32"
)

var _ Mat = &Mat2{}
var _ fmt.Stringer = &Mat2{}

type Mat2 struct {
	*blas32.General
}

func (m *Mat2) At(row, col int) float32 {
	return m.Data[row*2+col]
}

func (m *Mat2) Set(row, col int, val float32) {
	m.Data[row*2+col] = val
}

func (m *Mat2) Size() MatSize {
	return MatSize2x2
}

func (m *Mat2) String() string {
	return fmt.Sprintf("| %f %f |\n| %f %f |", m.Data[0], m.Data[1], m.Data[2], m.Data[3])
}

//Add m += m2
func (m *Mat2) Add(m2 *Mat2) {
	m.Data[0] += m2.Data[0]
	m.Data[1] += m2.Data[1]
	m.Data[2] += m2.Data[2]
	m.Data[3] += m2.Data[3]
}

//Add m -= m2
func (m *Mat2) Sub(m2 *Mat2) {
	m.Data[0] -= m2.Data[0]
	m.Data[1] -= m2.Data[1]
	m.Data[2] -= m2.Data[2]
	m.Data[3] -= m2.Data[3]
}

//Scale m *= x (element wise multiplication)
func (m *Mat2) Scale(x float32) {
	m.Data[0] *= x
	m.Data[1] *= x
	m.Data[2] *= x
	m.Data[3] *= x
}

//AddMat2 m3 = m1 + m2
func AddMat2(m1, m2 *Mat2) *Mat2 {
	return NewMat2([]float32{
		m1.Data[0] + m2.Data[0],
		m1.Data[1] + m2.Data[1],
		m1.Data[2] + m2.Data[2],
		m1.Data[3] + m2.Data[3],
	})
}

//SubMat2 m3 = m1 - m2
func SubMat2(m1, m2 *Mat2) *Mat2 {
	return NewMat2([]float32{
		m1.Data[0] - m2.Data[0],
		m1.Data[1] - m2.Data[1],
		m1.Data[2] - m2.Data[2],
		m1.Data[3] - m2.Data[3],
	})
}

//NewMat2 returns the identity matrix if data=nil, otherwise data is used
//as the backing array.
//
//Note: data must be row major
func NewMat2(data []float32) *Mat2 {

	if data == nil {
		data = []float32{
			1, 0,
			0, 1,
		}
	} else if len(data) != 4 {
		panic("Data must be nil or size 4")
	}

	return &Mat2{
		General: &blas32.General{
			Rows:   2,
			Cols:   2,
			Stride: 2,
			Data:   data,
		},
	}
}