Program f07mjfe
! F07MJF Example Program Text
! Mark 29.2 Release. NAG Copyright 2023.
! .. Use Statements ..
Use nag_library, Only: dsytrf, dsytri, nag_wp, x04caf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, lda, lwork, n
Character (1) :: uplo
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: a(:,:), work(:)
Integer, Allocatable :: ipiv(:)
! .. Executable Statements ..
Write (nout,*) 'F07MJF 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,*) uplo
If (uplo=='U') Then
Read (nin,*)(a(i,i:n),i=1,n)
Else If (uplo=='L') Then
Read (nin,*)(a(i,1:i),i=1,n)
End If
! Factorize A
! The NAG name equivalent of dsytrf is f07mdf
Call dsytrf(uplo,n,a,lda,ipiv,work,lwork,info)
Write (nout,*)
Flush (nout)
If (info==0) Then
! Compute inverse of A
! The NAG name equivalent of dsytri is f07mjf
Call dsytri(uplo,n,a,lda,ipiv,work,info)
! Print inverse
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04caf(uplo,'Nonunit',n,n,a,lda,'Inverse',ifail)
Else
Write (nout,*) 'The factor D is singular'
End If
End Program f07mjfe