PROGRAM f07bafe ! F07BAF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dgbsv, nag_wp, x04cef ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: i, ifail, info, j, k, kl, ku, ldab, n ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: ab(:,:), b(:) INTEGER, ALLOCATABLE :: ipiv(:) ! .. Intrinsic Functions .. INTRINSIC max, min ! .. Executable Statements .. WRITE (nout,*) 'F07BAF Example Program Results' WRITE (nout,*) ! Skip heading in data file READ (nin,*) READ (nin,*) n, kl, ku ldab = 2*kl + ku + 1 ALLOCATE (ab(ldab,n),b(n),ipiv(n)) ! Read the band matrix A and the right hand side b from data file k = kl + ku + 1 READ (nin,*) ((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,n)),i=1,n) READ (nin,*) b(1:n) ! Solve the equations Ax = b for x ! The NAG name equivalent of dgbsv is f07baf CALL dgbsv(n,kl,ku,1,ab,ldab,ipiv,b,n,info) IF (info==0) THEN ! Print solution WRITE (nout,*) 'Solution' WRITE (nout,99999) b(1:n) ! Print details of the factorization WRITE (nout,*) FLUSH (nout) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 CALL x04cef(n,n,kl,kl+ku,ab,ldab,'Details of factorization',ifail) ! Print pivot indices' WRITE (nout,*) WRITE (nout,*) 'Pivot indices' WRITE (nout,99998) ipiv(1:n) ELSE WRITE (nout,99997) 'The (', info, ',', info, ')', & ' element of the factor U is zero' END IF 99999 FORMAT ((3X,7F11.4)) 99998 FORMAT ((3X,7I11)) 99997 FORMAT (1X,A,I3,A,I3,A,A) END PROGRAM f07bafe