Program f07pefe
! F07PEF Example Program Text
! Mark 28.7 Release. NAG Copyright 2022.
! .. Use Statements ..
Use nag_library, Only: dsptrf, dsptrs, nag_wp, x04caf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, j, ldb, n, nrhs
Character (1) :: uplo
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: ap(:), b(:,:)
Integer, Allocatable :: ipiv(:)
! .. Executable Statements ..
Write (nout,*) 'F07PEF Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) n, nrhs
ldb = n
Allocate (ap(n*(n+1)/2),b(ldb,nrhs),ipiv(n))
! Read A and B from data file
Read (nin,*) uplo
If (uplo=='U') Then
Read (nin,*)((ap(i+j*(j-1)/2),j=i,n),i=1,n)
Else If (uplo=='L') Then
Read (nin,*)((ap(i+(2*n-j)*(j-1)/2),j=1,i),i=1,n)
End If
Read (nin,*)(b(i,1:nrhs),i=1,n)
! Factorize A
! The NAG name equivalent of dsptrf is f07pdf
Call dsptrf(uplo,n,ap,ipiv,info)
Write (nout,*)
Flush (nout)
If (info==0) Then
! Compute solution
! The NAG name equivalent of dsptrs is f07pef
Call dsptrs(uplo,n,nrhs,ap,ipiv,b,ldb,info)
! Print solution
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04caf('General',' ',n,nrhs,b,ldb,'Solution(s)',ifail)
Else
Write (nout,*) 'The factor D is singular'
End If
End Program f07pefe