Program f04bcfe ! F04BCF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: f04bcf, nag_wp, x04caf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: errbnd, rcond Integer :: i, ierr, ifail, ldb, n, nrhs ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: b(:,:), d(:), dl(:), du(:), du2(:) Integer, Allocatable :: ipiv(:) ! .. Executable Statements .. Write (nout,*) 'F04BCF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs ldb = n Allocate (b(ldb,nrhs),d(n),dl(n-1),du(n-1),du2(n-2),ipiv(n)) ! Read A and B from data file Read (nin,*) du(1:n-1) Read (nin,*) d(1:n) Read (nin,*) dl(1:n-1) Read (nin,*)(b(i,1:nrhs),i=1,n) ! Solve the equations AX = B for X ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 1 Call f04bcf(n,nrhs,dl,d,du,du2,ipiv,b,ldb,rcond,errbnd,ifail) If (ifail==0) Then ! Print solution, estimate of condition number and approximate ! error bound ierr = 0 Call x04caf('General',' ',n,nrhs,b,ldb,'Solution',ierr) Write (nout,*) Write (nout,*) 'Estimate of condition number' Write (nout,99999) 1.0E0_nag_wp/rcond Write (nout,*) Write (nout,*) 'Estimate of error bound for computed solutions' Write (nout,99999) errbnd Else If (ifail==n+1) Then ! Matrix A is numerically singular. Print estimate of ! reciprocal of condition number and solution Write (nout,*) Write (nout,*) 'Estimate of reciprocal of condition number' Write (nout,99999) rcond Write (nout,*) Flush (nout) ierr = 0 Call x04caf('General',' ',n,nrhs,b,ldb,'Solution',ierr) Else If (ifail>0 .And. ifail<=n) Then ! The upper triangular matrix U is exactly singular. Print ! details of factorization Write (nout,*) 'Details of factorization' Write (nout,*) Write (nout,*) ' Second super-diagonal of U' Write (nout,99998) du2(1:n-2) Write (nout,*) Write (nout,*) ' First super-diagonal of U' Write (nout,99998) du(1:n-1) Write (nout,*) Write (nout,*) ' Main diagonal of U' Write (nout,99998) d(1:n) Write (nout,*) Write (nout,*) ' Multipliers' Write (nout,99998) dl(1:n-1) Write (nout,*) Write (nout,*) ' Vector of interchanges' Write (nout,99997) ipiv(1:n) Else Write (nout,99996) ifail End If 99999 Format (6X,1P,E9.1) 99998 Format (1X,8F9.4) 99997 Format (1X,8I9) 99996 Format (1X,' ** F04BCF returned with IFAIL = ',I5) End Program f04bcfe