Program dsgesv_example
! DSGESV Example Program Text
! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com
! .. Use Statements ..
Use lapack_interfaces, Only: dsgesv
Use lapack_precision, Only: sp, dp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Integer :: i, info, iter, lda, ldb, ldx, n, r
! .. Local Arrays ..
Real (Kind=dp), Allocatable :: a(:, :), b(:, :), work(:), x(:, :)
Real (Kind=sp), Allocatable :: swork(:)
Integer, Allocatable :: ipiv(:)
! .. Executable Statements ..
Write (nout, *) 'DSGESV Example Program Results'
Write (nout, *)
! Skip heading in data file
Read (nin, *)
Read (nin, *) n, r
lda = n
ldb = n
ldx = n
Allocate (a(lda,n), b(n,r), work(n*r), x(ldx,r), swork(n*(n+ &
r)), ipiv(n))
! Read A and B from data file
Read (nin, *)(a(i,1:n), i=1, n)
Read (nin, *)(b(i,1:r), i=1, n)
! Solve the equations Ax = b for x
Call dsgesv(n, r, a, lda, ipiv, b, ldb, x, ldx, work, swork, iter, info)
If (info==0) Then
! Print solution
Write (nout, *) 'Solution'
Write (nout, 100)(x(i,1:r), i=1, n)
! Print pivot indices
Write (nout, *)
Write (nout, *) 'Pivot indices'
Write (nout, 110) ipiv(1:n)
Else
Write (nout, 120) 'The (', info, ',', info, ')', &
' element of the factor U is zero'
End If
100 Format ((3X,7F11.4))
110 Format ((3X,7I11))
120 Format (1X, A, I3, A, I3, A, A)
End Program