Program f07bbfe ! F07BBF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dgbsvx, 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, j, k, kl, ku, ldab, & ldafb, ldb, ldx, n, nrhs Character (1) :: equed ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), afb(:,:), b(:,:), berr(:), & c(:), ferr(:), r(:), work(:), x(:,:) Integer, Allocatable :: ipiv(:), iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F07BBF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs, kl, ku ldb = n ldx = n ldab = kl + ku + 1 ldafb = ldab + kl Allocate (ab(ldab,n),afb(ldafb,n),b(ldb,nrhs),berr(nrhs),c(n), & ferr(nrhs),r(n),work(3*n),x(ldx,nrhs),ipiv(n),iwork(n)) ! Read the band matrix A and B from data file k = ku + 1 Read (nin,*)((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,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 dgbsvx is f07bbf Call dgbsvx('Equilibration','No transpose',n,kl,ku,nrhs,ab,ldab,afb, & ldafb,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,*) 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=='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,*) '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 f07bbfe