Program dgbtrs_example ! DGBTRS 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: dgbtrf, dgbtrs Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: trans = 'N' ! .. Local Scalars .. Integer :: i, ifail, info, j, k, kl, ku, ldab, ldb, n, nrhs ! .. Local Arrays .. Real (Kind=dp), Allocatable :: ab(:, :), b(:, :) Integer, Allocatable :: ipiv(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout, *) 'DGBTRS Example Program Results' ! Skip heading in data file Read (nin, *) Read (nin, *) n, nrhs, kl, ku ldab = 2*kl + ku + 1 ldb = n Allocate (ab(ldab,n), b(ldb,nrhs), ipiv(n)) ! Read A and B from data file k = kl + ku + 1 Read (nin, *)((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,n)), i=1, n) Read (nin, *)(b(i,1:nrhs), i=1, n) ! Factorize A Call dgbtrf(n, n, kl, ku, ab, ldab, ipiv, info) Write (nout, *) Flush (nout) If (info==0) Then ! Compute solution Call dgbtrs(trans, n, kl, ku, nrhs, ab, ldab, ipiv, b, ldb, info) ! Print solution ! 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, b, ldb, & 'Solution(s)', ifail) Else Write (nout, *) 'The factor U is singular' End If End Program