Program f11mhfe
! F11MHF Example Program Text
! Mark 30.3 Release. nAG Copyright 2024.
! .. Use Statements ..
Use nag_library, Only: f11mdf, f11mef, f11mff, f11mhf, nag_wp, x04caf, &
x04cbf
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Real (Kind=nag_wp), Parameter :: one = 1.E0_nag_wp
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Real (Kind=nag_wp) :: flop, thresh
Integer :: i, ifail, j, ldb, ldx, n, nnz, nnzl, &
nnzu, nrhs, nzlmx, nzlumx, nzumx
Character (1) :: spec, trans
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: a(:), b(:,:), berr(:), ferr(:), &
lval(:), uval(:), x(:,:)
Integer, Allocatable :: icolzp(:), il(:), iprm(:), &
irowix(:), iu(:)
Character (1) :: clabs(1), rlabs(1)
! .. Executable Statements ..
Write (nout,*) 'F11MHF Example Program Results'
Flush (nout)
! Skip heading in data file
Read (nin,*)
! Read order of matrix and number of right hand sides
Read (nin,*) n, nrhs
ldb = n
ldx = n
Allocate (b(ldb,nrhs),berr(nrhs),ferr(nrhs),x(ldx,nrhs),icolzp(n+1), &
iprm(7*n))
! Read the matrix A
Read (nin,*) icolzp(1:n+1)
nnz = icolzp(n+1) - 1
Allocate (a(nnz),lval(8*nnz),uval(8*nnz),il(7*n+8*nnz+4),irowix(nnz), &
iu(2*n+8*nnz+1))
Do i = 1, nnz
Read (nin,*) a(i), irowix(i)
End Do
! Read the right hand sides
Do j = 1, nrhs
Read (nin,*) x(1:n,j)
b(1:n,j) = x(1:n,j)
End Do
! Calculate COLAMD permutation
spec = 'M'
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call f11mdf(spec,n,icolzp,irowix,iprm,ifail)
! Factorise
thresh = one
ifail = 0
nzlmx = 8*nnz
nzlumx = 8*nnz
nzumx = 8*nnz
Call f11mef(n,irowix,a,iprm,thresh,nzlmx,nzlumx,nzumx,il,lval,iu,uval, &
nnzl,nnzu,flop,ifail)
! Compute solution in array X
trans = 'N'
ifail = 0
Call f11mff(trans,n,iprm,il,lval,iu,uval,nrhs,x,ldx,ifail)
! Improve solution, and compute backward errors and estimated
! bounds on the forward errors
Call f11mhf(trans,n,icolzp,irowix,a,iprm,il,lval,iu,uval,nrhs,b,ldb,x, &
ldx,ferr,berr,ifail)
! Print solution
Write (nout,*)
Flush (nout)
Call x04caf('G',' ',n,nrhs,x,ldx,'Solutions',ifail)
Call x04cbf('G','X',nrhs,1,ferr,nrhs,'1PE8.1','Estimated Forward Error', &
'N',rlabs,'N',clabs,80,0,ifail)
Call x04cbf('G','X',nrhs,1,berr,nrhs,'1PE8.1','Backward Error','N', &
rlabs,'N',clabs,80,0,ifail)
End Program f11mhfe