Program f07thfe ! F07THF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dtrrfs, dtrtrs, 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, lda, ldb, ldx, n, nrhs Character (1) :: uplo ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: a(:,:), b(:,:), berr(:), ferr(:), & work(:), x(:,:) Integer, Allocatable :: iwork(:) ! .. Executable Statements .. Write (nout,*) 'F07THF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs lda = n ldb = n ldx = n Allocate (a(lda,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 Read (nin,*)(a(i,i:n),i=1,n) Else If (uplo=='L') Then Read (nin,*)(a(i,1:i),i=1,n) 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 dtrtrs is f07tef Call dtrtrs(uplo,trans,diag,n,nrhs,a,lda,x,ldx,info) ! Compute backward errors and estimated bounds on the ! forward errors ! The NAG name equivalent of dtrrfs is f07thf Call dtrrfs(uplo,trans,diag,n,nrhs,a,lda,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 f07thfe