linsolve: for sparse matrix

[Konstantin8105]

Hello,

Now, design in linsolve/iterative.go is:

func Iterative(a MulVecToer, b *mat.VecDense, ...

Matrix a have matrix interface:

type MulVecToer interface {
	// MulVecTo computes A*x or Aᵀ*x and stores the result into dst.
	MulVecTo(dst *mat.VecDense, trans bool, x mat.Vector)
}

For my sparse matrix in my rep cannot implement that interface MulVecToer.

Could you replace type of variable a into type func(trans bool, x mat.Vector).
So, example linsolve/iterative_example_test.go look like:

...


ATx := func(trans bool, x mat.Vector){
       a.MulVecTo(mat.NewVecDense(dim, nil), trans, x)
}
result, err := linsolve.Iterative(ATx, sys.B, &linsolve.CG{}, nil)
if err != nil {
	fmt.Println("Error:", err)
	return
}

...

So, design in linsolve/iterative.go in my point of view:

func Iterative(a func(trans bool, x mat.Vector), b *mat.VecDense, ...

Feel free for ignore.

[Konstantin8105]

Excuse me, I find the solution without changes