Program f07btfe
! F07BTF Example Program Text
! Mark 28.6 Release. NAG Copyright 2022.
! .. Use Statements ..
Use nag_library, Only: f06kcf, nag_wp, x02ajf, x02amf, x02bhf, x04def, &
zdscal, zgbequ
! .. 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, colcnd, rowcnd, small
Integer :: i, i0, i1, ifail, ilen, info, j, k, &
kl, ku, ldab, n
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ab(:,:)
Real (Kind=nag_wp), Allocatable :: c(:), r(:)
! .. Intrinsic Procedures ..
Intrinsic :: max, min, real
! .. Executable Statements ..
Write (nout,*) 'F07BTF Example Program Results'
Write (nout,*)
Flush (nout)
! Skip heading in data file
Read (nin,*)
Read (nin,*) n, kl, ku
ldab = kl + ku + 1
Allocate (ab(ldab,n),c(n),r(n))
! Read the band matrix A from data file
k = ku + 1
Read (nin,*)((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,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 x04def(n,n,kl,ku,ab,ldab,'Matrix A',ifail)
Write (nout,*)
! Compute row and column scaling factors
! The NAG name equivalent of zgbequ is f07btf
Call zgbequ(n,n,kl,ku,ab,ldab,r,c,rowcnd,colcnd,amax,info)
If (info>0) Then
If (info<=n) Then
Write (nout,99999) 'Row ', info, ' of A is exactly zero'
Else
Write (nout,99999) 'Column ', info - n, ' of A is exactly zero'
End If
Else
! Print ROWCND, COLCND, AMAX and the scale factors
Write (nout,99998) 'ROWCND =', rowcnd, ', COLCND =', colcnd, &
', AMAX =', amax
Write (nout,*)
Write (nout,*) 'Row scale factors'
Write (nout,99997) r(1:n)
Write (nout,*)
Write (nout,*) 'Column scale factors'
Write (nout,99997) c(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 ((rowcnd>=thresh) .And. (amax>=small) .And. (amax<=big)) Then
If (colcnd<thresh) Then
! Just column scale A
! The NAG name equivalent of zdscal is f06jdf
Do j = 1, n
i1 = 1 + max(1,j-ku) - (j-ku)
ilen = min(n,j+kl) - max(1,j-ku) + 1
Call zdscal(ilen,c(j),ab(i1,j),1)
End Do
End If
Else If (colcnd>=thresh) Then
! Just row scale A
Do j = 1, n
i0 = max(1,j-ku)
i1 = 1 + i0 - (j-ku)
ilen = min(n,j+kl) - i0 + 1
Call f06kcf(ilen,r(i0),1,ab(i1,j),1)
End Do
Else
! Row and column scale A
Do j = 1, n
i0 = max(1,j-ku)
i1 = 1 + i0 - (j-ku)
ilen = min(n,j+kl) - i0 + 1
Call zdscal(ilen,c(j),ab(i1,j),1)
Call f06kcf(ilen,r(i0),1,ab(i1,j),1)
End Do
End If
! Print the scaled matrix
ifail = 0
Call x04def(n,n,kl,ku,ab,ldab,'Scaled matrix',ifail)
End If
99999 Format (1X,A,I4,A)
99998 Format (1X,3(A,1P,E8.1))
99997 Format ((1X,1P,7E11.2))
End Program f07btfe