Program zptsv_example ! ZPTSV Example Program Text ! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com ! .. Use Statements .. Use lapack_interfaces, Only: zptsv Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: info, n ! .. Local Arrays .. Complex (Kind=dp), Allocatable :: b(:), e(:) Real (Kind=dp), Allocatable :: d(:) ! .. Executable Statements .. Write (nout, *) 'ZPTSV Example Program Results' Write (nout, *) ! Skip heading in data file Read (nin, *) Read (nin, *) n Allocate (b(n), e(n-1), d(n)) ! Read the lower bidiagonal part of the tridiagonal matrix A and ! the right hand side b from data file Read (nin, *) d(1:n) Read (nin, *) e(1:n-1) Read (nin, *) b(1:n) ! Solve the equations Ax = b for x Call zptsv(n, 1, d, e, b, n, info) If (info==0) Then ! Print solution Write (nout, *) 'Solution' Write (nout, 100) b(1:n) ! Print details of factorization Write (nout, *) Write (nout, *) 'Diagonal elements of the diagonal matrix D' Write (nout, 110) d(1:n) Write (nout, *) Write (nout, *) 'Subdiagonal elements of the Cholesky factor L' Write (nout, 100) e(1:n-1) Else Write (nout, 120) 'The leading minor of order ', info, & ' is not positive definite' End If 100 Format (4(' (',F8.4,',',F8.4,')',:)) 110 Format ((2X,F7.4,3(11X,F7.4))) 120 Format (1X, A, I3, A) End Program