Program f07wwfe
! F07WWF Example Program Text
! Mark 30.2 Release. NAG Copyright 2024.
! .. Use Statements ..
Use nag_library, Only: nag_wp, x04dbf, zpftrf, zpftri, ztfttr
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, k, lar1, lda, lenar, &
n, q
Character (1) :: transr, uplo
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:,:), ar(:)
Character (1) :: clabs(1), rlabs(1)
! .. Executable Statements ..
Write (nout,*) 'F07WWF Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) n, uplo, transr
lenar = n*(n+1)/2
lda = n
Allocate (ar(lenar),a(lda,n))
! Setup notional dimensions of RFP matrix AR
k = n/2
q = n - k
If (transr=='N' .Or. transr=='n') Then
lar1 = 2*k + 1
Else
lar1 = q
End If
! Read an RFP matrix into array AR
Do i = 1, lar1
Read (nin,*) ar(i:lenar:lar1)
End Do
! Factorize A
! The NAG name equivalent of zpftrf is f07wrf
Call zpftrf(transr,uplo,n,ar,info)
Write (nout,*)
Flush (nout)
If (info==0) Then
! Compute inverse of A
! The NAG name equivalent of zpftri is f07wwf
Call zpftri(transr,uplo,n,ar,info)
! Convert and print inverse
! The NAG name equivalent of ztfttr is f01vhf
Call ztfttr(transr,uplo,n,ar,a,lda,info)
ifail = 0
Call x04dbf(uplo,'Nonunit',n,n,a,lda,'Bracketed','F7.4','Inverse', &
'Integer',rlabs,'Integer',clabs,80,0,ifail)
Else
Write (nout,*) 'A is not positive definite'
End If
End Program f07wwfe