How do I multiply a matrix with a vector in gonum?

Question

I want to multiply a mat.Dense Matrix with a mat.VecDense Vector, but obviously mat.Dense nor mat.VecDens do not implement the Matrix interface or define a method to multiply a matrix with a vector. How would I do that?

Answer 1

Solved it.

mat.NewVecDense(...) returns a *mat.VecDense, that implements a method func MulVec(a mat.Matrix, b mat.Vector)

Here is a test to validate the functionality

func TestMatrixVectorMul(t *testing.T) {
    a := mat.NewDense(3, 3, []float64{
        1, 2, 3, 4, 5, 6, 7, 8, 9,
    })
    b := mat.NewVecDense(3, []float64{
        1, 2, 3,
    })
    actual := make([]float64, 3)
    c := mat.NewVecDense(3, actual)

    // this was the method, I was looking for. 
    c.MulVec(a, b)
    expected := []float64{14, 32, 50}
    assert.Equal(t, expected, actual)
}