Program f07jbfe ! F07JBF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dptsvx, 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, ldb, ldx, n, nrhs ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: b(:,:), berr(:), d(:), df(:), e(:), & ef(:), ferr(:), work(:), x(:,:) ! .. Executable Statements .. Write (nout,*) 'F07JBF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs ldb = n ldx = n Allocate (b(ldb,nrhs),berr(nrhs),d(n),df(n),e(n-1),ef(n-1),ferr(nrhs), & work(2*n),x(ldx,nrhs)) ! Read the lower bidiagonal part of the tridiagonal matrix A and ! the right hand side b from data file Read (nin,*) d(1:n) Read (nin,*) e(1:n-1) Read (nin,*)(b(i,1:nrhs),i=1,n) ! Solve the equations AX = B for X ! The NAG name equivalent of dptsvx is f07jbf Call dptsvx('Not factored',n,nrhs,d,e,df,ef,b,ldb,x,ldx,rcond,ferr,berr, & work,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 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 (1X,1P,7E11.1) 99998 Format (1X,A,I3,A) End Program f07jbfe