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