Program dtbtrs_example
! DTBTRS 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: dtbtrs
Use lapack_precision, Only: dp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
Character (1), Parameter :: diag = 'N', trans = 'N'
! .. Local Scalars ..
Integer :: i, ifail, info, j, kd, ldab, ldb, n, nrhs
Character (1) :: uplo
! .. Local Arrays ..
Real (Kind=dp), Allocatable :: ab(:, :), b(:, :)
! .. Intrinsic Procedures ..
Intrinsic :: max, min
! .. Executable Statements ..
Write (nout, *) 'DTBTRS Example Program Results'
! Skip heading in data file
Read (nin, *)
Read (nin, *) n, kd, nrhs
ldab = kd + 1
ldb = n
Allocate (ab(ldab,n), b(ldb,nrhs))
! Read A and B from data file
Read (nin, *) uplo
If (uplo=='U') Then
Do i = 1, n
Read (nin, *)(ab(kd+1+i-j,j), j=i, min(n,i+kd))
End Do
Else If (uplo=='L') Then
Do i = 1, n
Read (nin, *)(ab(1+i-j,j), j=max(1,i-kd), i)
End Do
End If
Read (nin, *)(b(i,1:nrhs), i=1, n)
! Compute solution
Call dtbtrs(uplo, trans, diag, n, kd, nrhs, ab, ldab, b, ldb, info)
! Print solution
Write (nout, *)
Flush (nout)
If (info==0) Then
! 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, *) 'A is singular'
End If
End Program