Tridiagonal Interface

public interface Tridiagonal

This interface provides different methods to construct a Tridiagonal matrix. Only the non-zero elements of $A$ are stored, i.e.

$$A = \begin{bmatrix} a_1 & b_1 \\ c_1 & a_2 & b_2 \\ & \ddots & \ddots & \ddots \\ & & c_{n-2} & a_{n-1} & b_{n-1} \\ & & & c_{n-1} & a_n \end{bmatrix}.$$

Syntax

• Construct a Tridiagonal matrix filled with zeros:

   integer, parameter :: n = 100
   type(Tridiagonal) :: A

   A = Tridiagonal(n)

• Construct a Tridiagonal matrix from rank-1 arrays:

   integer, parameter :: n
   real(dp), allocatable :: dl(:), dv(:), du(:)
   type(Tridiagonal) :: A
   integer :: i

   dl = [(i, i=1, n-1)]; dv = [(2*i, i=1, n)]; du = [(3*i, i=1, n)]
   A = Tridiagonal(dl, dv, du)

• Construct a Tridiagonal matrix with constant diagonals:

   integer, parameter :: n
   real(dp), parameter :: a = 1.0_dp, b = 1.0_dp, c = 2.0_dp
   type(Tridiagonal) :: A

   A = Tridiagonal(a, b, c, n)

Functions