Program f07aafe
! F07AAF Example Program Text
! Mark 26.2 Release. NAG Copyright 2017.
! .. Use Statements ..
Use nag_library, Only: dgesv, nag_wp, x04caf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, ifail, info, lda, ldb, n
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: a(:,:), b(:)
Integer, Allocatable :: ipiv(:)
! .. Executable Statements ..
Write (nout,*) 'F07AAF Example Program Results'
Write (nout,*)
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
lda = n
ldb = n
Allocate (a(lda,n),b(ldb),ipiv(n))
! Read A and B from data file
Read (nin,*)(a(i,1:n),i=1,n)
Read (nin,*) b(1:n)
! Solve the equations Ax = b for x
! The NAG name equivalent of dgesv is f07aaf
Call dgesv(n,1,a,lda,ipiv,b,ldb,info)
If (info==0) Then
! Print solution
Write (nout,*) 'Solution'
Write (nout,99999) b(1:n)
! Print details of factorization
Write (nout,*)
Flush (nout)
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call x04caf('General',' ',n,n,a,lda,'Details of factorization',ifail)
! Print pivot indices
Write (nout,*)
Write (nout,*) 'Pivot indices'
Write (nout,99998) ipiv(1:n)
Else
Write (nout,99997) 'The (', info, ',', info, ')', &
' element of the factor U is zero'
End If
99999 Format ((3X,7F11.4))
99998 Format ((3X,7I11))
99997 Format (1X,A,I3,A,I3,A,A)
End Program f07aafe