PROGRAM f07hbfe ! F07HBF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dpbsvx, nag_wp, x04caf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 CHARACTER (1), PARAMETER :: uplo = 'U' ! .. Local Scalars .. REAL (KIND=nag_wp) :: rcond INTEGER :: i, ifail, info, j, kd, ldab, ldafb, & ldb, ldx, n, nrhs CHARACTER (1) :: equed ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: ab(:,:), afb(:,:), b(:,:), berr(:), & ferr(:), s(:), work(:), x(:,:) INTEGER, ALLOCATABLE :: iwork(:) ! .. Intrinsic Functions .. INTRINSIC max, min ! .. Executable Statements .. WRITE (nout,*) 'F07HBF Example Program Results' WRITE (nout,*) FLUSH (nout) ! Skip heading in data file READ (nin,*) READ (nin,*) n, kd, nrhs ldb = n ldx = n ldab = kd + 1 ldafb = kd + 1 ALLOCATE (ab(ldab,n),afb(ldafb,n),b(ldb,nrhs),berr(nrhs),ferr(nrhs), & s(n),work(3*n),x(ldx,nrhs),iwork(n)) ! Read the upper or lower triangular part of the band matrix A ! from data file IF (uplo=='U') THEN READ (nin,*) ((ab(kd+1+i-j,j),j=i,min(n,i+kd)),i=1,n) ELSE IF (uplo=='L') THEN READ (nin,*) ((ab(1+i-j,j),j=max(1,i-kd),i),i=1,n) END IF ! 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 dpbsvx is f07hbf CALL dpbsvx('Equilibration',uplo,n,kd,nrhs,ab,ldab,afb,ldafb,equed,s,b, & ldb,x,ldx,rcond,ferr,berr,work,iwork,info) IF ((info==0) .OR. (info==n+1)) THEN ! Print solution, error bounds, condition number and the form ! of equilibration ! 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 (equed=='N') THEN WRITE (nout,*) 'A has not been equilibrated' ELSE IF (equed=='Y') THEN WRITE (nout,*) & 'A has been row and column scaled as diag(S)*A*diag(S)' END IF IF (info==n+1) THEN WRITE (nout,*) WRITE (nout,*) 'The matrix A is singular to working precision' END IF ELSE WRITE (nout,99998) 'The leading minor of order ', info, & ' is not positive definite' END IF 99999 FORMAT ((3X,1P,7E11.1)) 99998 FORMAT (1X,A,I3,A) END PROGRAM f07hbfe