PROGRAM f07abfe
! F07ABF Example Program Text
! Mark 23 Release. NAG Copyright 2011.
! .. Use Statements ..
USE nag_library, ONLY : dgesvx, nag_wp, x04caf
! .. Implicit None Statement ..
IMPLICIT NONE
! .. Parameters ..
INTEGER, PARAMETER :: nin = 5, nout = 6
! .. Local Scalars ..
REAL (KIND=nag_wp) :: rcond
INTEGER :: i, ifail, info, lda, ldaf, ldb, ldx, &
n, nrhs
CHARACTER (1) :: equed
! .. Local Arrays ..
REAL (KIND=nag_wp), ALLOCATABLE :: a(:,:), af(:,:), b(:,:), berr(:), &
c(:), ferr(:), r(:), work(:), x(:,:)
INTEGER, ALLOCATABLE :: ipiv(:), iwork(:)
! .. Executable Statements ..
WRITE (nout,*) 'F07ABF Example Program Results'
WRITE (nout,*)
FLUSH (nout)
! Skip heading in data file
READ (nin,*)
READ (nin,*) n, nrhs
lda = n
ldaf = n
ldb = n
ldx = n
ALLOCATE (a(lda,n),af(ldaf,n),b(ldb,nrhs),berr(nrhs),c(n),ferr(nrhs), &
r(n),work(4*n),x(ldx,nrhs),ipiv(n),iwork(n))
! Read A and B from data file
READ (nin,*) (a(i,1:n),i=1,n)
READ (nin,*) (b(i,1:nrhs),i=1,n)
! Solve the equations AX = B for X
! The NAG name equivalent of dgesvx is f07abf
CALL dgesvx('Equilibration','No transpose',n,nrhs,a,lda,af,ldaf,ipiv, &
equed,r,c,b,ldb,x,ldx,rcond,ferr,berr,work,iwork,info)
IF ((info==0) .OR. (info==n+1)) THEN
! Print solution, error bounds, condition number, the form
! of equilibration and the pivot growth factor
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
CALL x04caf('General',' ',n,nrhs,x,ldx,'Solution(s)',ifail)
WRITE (nout,*)
WRITE (nout,*) 'Backward errors (machine-dependent)'
WRITE (nout,99999) berr(1:nrhs)
WRITE (nout,*)
WRITE (nout,*) 'Estimated forward error bounds (machine-dependent)'
WRITE (nout,99999) ferr(1:nrhs)
WRITE (nout,*)
IF (equed=='N') THEN
WRITE (nout,*) 'A has not been equilibrated'
ELSE IF (equed=='R') THEN
WRITE (nout,*) 'A has been row scaled as diag(R)*A'
ELSE IF (equed=='C') THEN
WRITE (nout,*) 'A has been column scaled as A*diag(C)'
ELSE IF (equed=='B') THEN
WRITE (nout,*) &
'A has been row and column scaled as diag(R)*A*diag(C)'
END IF
WRITE (nout,*)
WRITE (nout,*) &
'Reciprocal condition number estimate of scaled matrix'
WRITE (nout,99999) rcond
WRITE (nout,*)
WRITE (nout,*) 'Estimate of reciprocal pivot growth factor'
WRITE (nout,99999) work(1)
IF (info==n+1) THEN
WRITE (nout,*)
WRITE (nout,*) 'The matrix A is singular to working precision'
END IF
ELSE
WRITE (nout,99998) 'The (', info, ',', info, ')', &
' element of the factor U is zero'
END IF
99999 FORMAT ((3X,1P,7E11.1))
99998 FORMAT (1X,A,I3,A,I3,A,A)
END PROGRAM f07abfe