Program dgetri_example
! DGETRI 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: dgetrf, dgetri
Use lapack_precision, Only: dp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, lda, lwork, n
! .. Local Arrays ..
Real (Kind=dp), Allocatable :: a(:, :), work(:)
Integer, Allocatable :: ipiv(:)
! .. Executable Statements ..
Write (nout, *) 'DGETRI Example Program Results'
! Skip heading in data file
Read (nin, *)
Read (nin, *) n
lda = n
lwork = 64*n
Allocate (a(lda,n), work(lwork), ipiv(n))
! Read A from data file
Read (nin, *)(a(i,1:n), i=1, n)
! Factorize A
Call dgetrf(n, n, a, lda, ipiv, info)
Write (nout, *)
Flush (nout)
If (info==0) Then
! Compute inverse of A
Call dgetri(n, a, lda, ipiv, work, lwork, info)
! Print inverse
! 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, n, a, lda, &
'Inverse', ifail)
Else
Write (nout, *) 'The factor U is singular'
End If
End Program