Program f07ftfe
! F07FTF Example Program Text
! Mark 30.1 Release. NAG Copyright 2024.
! .. Use Statements ..
Use nag_library, Only: f06kcf, nag_wp, x02ajf, x02amf, x02bhf, x04dbf, &
zdscal, zpoequ
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Real (Kind=nag_wp), Parameter :: one = 1.0_nag_wp
Real (Kind=nag_wp), Parameter :: thresh = 0.1_nag_wp
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Real (Kind=nag_wp) :: amax, big, scond, small
Integer :: i, ifail, info, j, lda, n
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:,:)
Real (Kind=nag_wp), Allocatable :: s(:)
Character (1) :: clabs(1), rlabs(1)
! .. Intrinsic Procedures ..
Intrinsic :: real
! .. Executable Statements ..
Write (nout,*) 'F07FTF Example Program Results'
Write (nout,*)
Flush (nout)
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
lda = n
Allocate (a(lda,n),s(n))
! Read the upper triangular part of the matrix A from data file
Read (nin,*)(a(i,i:n),i=1,n)
! Print the matrix A
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04dbf('Upper','Non-unit',n,n,a,lda,'Bracketed','1P,E10.2', &
'Matrix A','Integer',rlabs,'Integer',clabs,80,0,ifail)
Write (nout,*)
! Compute diagonal scaling factors
! The NAG name equivalent of zpoequ is f07ftf
Call zpoequ(n,a,lda,s,scond,amax,info)
If (info>0) Then
Write (nout,99999) 'Diagonal element', info, ' of A is non positive'
Else
! Print SCOND, AMAX and the scale factors
Write (nout,99998) 'SCOND =', scond, ', AMAX =', amax
Write (nout,*)
Write (nout,*) 'Diagonal scaling factors'
Write (nout,99997) s(1:n)
Write (nout,*)
Flush (nout)
! Compute values close to underflow and overflow
small = x02amf()/(x02ajf()*real(x02bhf(),kind=nag_wp))
big = one/small
If ((scond<thresh) .Or. (amax<small) .Or. (amax>big)) Then
! Scale A
! The NAG name equivalent of zdscal is f06jdf
Do j = 1, n
Call zdscal(j,s(j),a(1,j),1)
Call f06kcf(j,s,1,a(1,j),1)
End Do
! Print the scaled matrix
ifail = 0
Call x04dbf('Upper','Non-unit',n,n,a,lda,'Bracketed','F8.4', &
'Scaled matrix','Integer',rlabs,'Integer',clabs,80,0,ifail)
End If
End If
99999 Format (1X,A,I4,A)
99998 Format (1X,2(A,1P,E8.1))
99997 Format ((1X,1P,7E11.1))
End Program f07ftfe