PROGRAM f08znfe

!      F08ZNF Example Program Text

!      Mark 23 Release. NAG Copyright 2011.

!      .. Use Statements ..
       USE nag_library, ONLY : dznrm2, nag_wp, zgglse
!      .. Implicit None Statement ..
       IMPLICIT NONE
!      .. Parameters ..
       INTEGER, PARAMETER              :: nb = 64, nin = 5, nout = 6
!      .. Local Scalars ..
       REAL (KIND=nag_wp)              :: rnorm
       INTEGER                         :: i, info, lda, ldb, lwork, m, n, p
!      .. Local Arrays ..
       COMPLEX (KIND=nag_wp), ALLOCATABLE :: a(:,:), b(:,:), c(:), d(:),       &
                                             work(:), x(:)
!      .. Executable Statements ..
       WRITE (nout,*) 'F08ZNF Example Program Results'
       WRITE (nout,*)
!      Skip heading in data file
       READ (nin,*)
       READ (nin,*) m, n, p
       lda = m
       ldb = p
       lwork = p + n + nb*(m+n)
       ALLOCATE (a(lda,n),b(ldb,n),c(m),d(p),work(lwork),x(n))

!      Read A, B, C and D from data file

       READ (nin,*) (a(i,1:n),i=1,m)
       READ (nin,*) (b(i,1:n),i=1,p)
       READ (nin,*) c(1:m)
       READ (nin,*) d(1:p)

!      Solve the equality-constrained least-squares problem

!      minimize ||c - A*x|| (in the 2-norm) subject to B*x = D

!      The NAG name equivalent of zgglse is f08znf
       CALL zgglse(m,n,p,a,lda,b,ldb,c,d,x,work,lwork,info)

!      Print least-squares solution

       WRITE (nout,*) 'Constrained least-squares solution'
       WRITE (nout,99999) x(1:n)

!      Compute the square root of the residual sum of squares

!      The NAG name equivalent of dznrm2 is f06jjf
       rnorm = dznrm2(m-n+p,c(n-p+1),1)
       WRITE (nout,*)
       WRITE (nout,*) 'Square root of the residual sum of squares'
       WRITE (nout,99998) rnorm

99999  FORMAT (4(' (',F7.4,',',F7.4,')':))
99998  FORMAT (1X,1P,E10.2)
    END PROGRAM f08znfe