PROGRAM f07mbfe ! F07MBF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dsysvx, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nb = 64, nin = 5, nout = 6 ! .. Local Scalars .. REAL (KIND=nag_wp) :: rcond INTEGER :: i, ifail, info, lda, ldaf, ldb, ldx, & lwork, n, nrhs ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: a(:,:), af(:,:), b(:,:), berr(:), & ferr(:), work(:), x(:,:) INTEGER, ALLOCATABLE :: ipiv(:), iwork(:) ! .. Executable Statements .. WRITE (nout,*) 'F07MBF 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 lwork = nb*n ALLOCATE (a(lda,n),af(ldaf,n),b(ldb,nrhs),berr(nrhs),ferr(nrhs), & work(lwork),x(ldx,nrhs),ipiv(n),iwork(n)) ! Read the upper triangular part of A from data file READ (nin,*) (a(i,i:n),i=1,n) ! Read B from data file READ (nin,*) (b(i,1:nrhs),i=1,n) ! Solve the equations AX = B for X ! The NAG name equivalent of dsysvx is f07mbf CALL dsysvx('Not factored','Upper',n,nrhs,a,lda,af,ldaf,ipiv,b,ldb,x, & ldx,rcond,ferr,berr,work,lwork,iwork,info) IF ((info==0) .OR. (info==n+1)) THEN ! Print solution, error bounds and condition number ! 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,*) WRITE (nout,*) 'Estimate of reciprocal condition number' WRITE (nout,99999) rcond WRITE (nout,*) IF (info==n+1) THEN WRITE (nout,*) WRITE (nout,*) 'The matrix A is singular to working precision' END IF ELSE WRITE (nout,99998) 'The diagonal block ', info, ' of D is zero' END IF 99999 FORMAT ((3X,1P,7E11.1)) 99998 FORMAT (1X,A,I3,A) END PROGRAM f07mbfe