Program dptsvx_example ! DPTSVX Example Program Text ! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com ! .. Use Statements .. Use lapack_example_aux, Only: nagf_file_print_matrix_real_gen Use lapack_interfaces, Only: dptsvx Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=dp) :: rcond Integer :: i, ifail, info, ldb, ldx, n, nrhs ! .. Local Arrays .. Real (Kind=dp), Allocatable :: b(:, :), berr(:), d(:), df(:), e(:), & ef(:), ferr(:), work(:), x(:, :) ! .. Executable Statements .. Write (nout, *) 'DPTSVX Example Program Results' Write (nout, *) Flush (nout) ! Skip heading in data file Read (nin, *) Read (nin, *) n, nrhs ldb = n ldx = n Allocate (b(ldb,nrhs), berr(nrhs), d(n), df(n), e(n-1), ef(n-1), & ferr(nrhs), work(2*n), x(ldx,nrhs)) ! 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(i,1:nrhs), i=1, n) ! Solve the equations AX = B for X Call dptsvx('Not factored', n, nrhs, d, e, df, ef, b, ldb, x, ldx, & rcond, ferr, berr, work, info) If ((info==0) .Or. (info==n+1)) Then ! Print solution, error bounds and condition number ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call nagf_file_print_matrix_real_gen('General', ' ', n, nrhs, x, ldx, & 'Solution(s)', ifail) Write (nout, *) Write (nout, *) 'Backward errors (machine-dependent)' Write (nout, 100) berr(1:nrhs) Write (nout, *) Write (nout, *) 'Estimated forward error bounds (machine-dependent)' Write (nout, 100) ferr(1:nrhs) Write (nout, *) Write (nout, *) 'Estimate of reciprocal condition number' Write (nout, 100) rcond If (info==n+1) Then Write (nout, *) Write (nout, *) 'The matrix A is singular to working precision' End If Else Write (nout, 110) 'The leading minor of order ', info, & ' is not positive definite' End If 100 Format (1X, 1P, 7E11.1) 110 Format (1X, A, I3, A) End Program