Program f07mhfe ! F07MHF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dsyrfs, dsytrf, dsytrs, nag_wp, x04caf ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Integer :: i, ifail, info, lda, ldaf, ldb, ldx, & lwork, n, nrhs Character (1) :: uplo ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: a(:,:), af(:,:), b(:,:), berr(:), & ferr(:), work(:), x(:,:) Integer, Allocatable :: ipiv(:), iwork(:) ! .. Executable Statements .. Write (nout,*) 'F07MHF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) n, nrhs lda = n ldaf = n ldb = n ldx = n lwork = 64*n Allocate (a(lda,n),af(ldaf,n),b(ldb,nrhs),berr(nrhs),ferr(nrhs), & work(lwork),x(ldx,n),ipiv(n),iwork(n)) ! Read A and B from data file, and copy A to AF and B to X Read (nin,*) uplo If (uplo=='U') Then Do i = 1, n Read (nin,*) a(i,i:n) af(i,i:n) = a(i,i:n) End Do Else If (uplo=='L') Then Do i = 1, n Read (nin,*) a(i,1:i) af(i,1:i) = a(i,1:i) End Do End If Read (nin,*)(b(i,1:nrhs),i=1,n) x(1:n,1:nrhs) = b(1:n,1:nrhs) ! Factorize A in the array AF ! The NAG name equivalent of dsytrf is f07mdf Call dsytrf(uplo,n,af,ldaf,ipiv,work,lwork,info) Write (nout,*) Flush (nout) If (info==0) Then ! Compute solution in the array X ! The NAG name equivalent of dsytrs is f07mef Call dsytrs(uplo,n,nrhs,af,ldaf,ipiv,x,ldx,info) ! Improve solution, and compute backward errors and ! estimated bounds on the forward errors ! The NAG name equivalent of dsyrfs is f07mhf Call dsyrfs(uplo,n,nrhs,a,lda,af,ldaf,ipiv,b,ldb,x,ldx,ferr,berr,work, & iwork,info) ! Print solution ! 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) Else Write (nout,*) 'The factor D is singular' End If 99999 Format ((3X,1P,7E11.1)) End Program f07mhfe