Program f07vhfe ! F07VHF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dtbrfs, dtbtrs, nag_wp, x04caf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 Character (1), Parameter :: diag = 'N', trans = 'N' ! .. Local Scalars .. Integer :: i, ifail, info, j, kd, ldab, ldb, & ldx, n, nrhs Character (1) :: uplo ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), b(:,:), berr(:), ferr(:), & work(:), x(:,:) Integer, Allocatable :: iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min ! .. Executable Statements .. Write (nout,*) 'F07VHF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, kd, nrhs ldab = kd + 1 ldb = n ldx = n Allocate (ab(ldab,n),b(ldb,nrhs),berr(nrhs),ferr(nrhs),work(3*n), & x(ldx,n),iwork(n)) ! Read A and B from data file, and copy B to X Read (nin,*) uplo If (uplo=='U') Then Do i = 1, n Read (nin,*)(ab(kd+1+i-j,j),j=i,min(n,i+kd)) End Do Else If (uplo=='L') Then Do i = 1, n Read (nin,*)(ab(1+i-j,j),j=max(1,i-kd),i) End Do End If Read (nin,*)(b(i,1:nrhs),i=1,n) x(1:n,1:nrhs) = b(1:n,1:nrhs) ! Compute solution in the array X ! The NAG name equivalent of dtbtrs is f07vef Call dtbtrs(uplo,trans,diag,n,kd,nrhs,ab,ldab,x,ldx,info) ! Compute backward errors and estimated bounds on the ! forward errors ! The NAG name equivalent of dtbrfs is f07vhf Call dtbrfs(uplo,trans,diag,n,kd,nrhs,ab,ldab,b,ldb,x,ldx,ferr,berr, & work,iwork,info) ! Print solution Write (nout,*) Flush (nout) ! 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,*) 'Estimated forward error bounds (machine-dependent)' Write (nout,99999) ferr(1:nrhs) 99999 Format ((3X,1P,7E11.1)) End Program f07vhfe