Program f11jefe
! F11JEF Example Program Text
! Mark 28.7 Release. NAG Copyright 2022.
! .. Use Statements ..
Use nag_library, Only: f11jef, nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Real (Kind=nag_wp) :: omega, rnorm, tol
Integer :: i, ifail, itn, lwork, maxitn, n, nnz
Character (6) :: method
Character (1) :: precon
! .. Local Arrays ..
Real (Kind=nag_wp), Allocatable :: a(:), b(:), work(:), x(:)
Integer, Allocatable :: icol(:), irow(:), iwork(:)
! .. Executable Statements ..
Write (nout,*) 'F11JEF Example Program Results'
! Skip heading in data file
Read (nin,*)
! Read algorithmic parameters
Read (nin,*) n
Read (nin,*) nnz
lwork = 7*n + 120
Allocate (a(nnz),b(n),work(lwork),x(n),icol(nnz),irow(nnz),iwork(n+1))
Read (nin,*) method, precon
Read (nin,*) omega
Read (nin,*) tol, maxitn
! Read the matrix A
Do i = 1, nnz
Read (nin,*) a(i), irow(i), icol(i)
End Do
! Read right-hand side vector b and initial approximate solution x
Read (nin,*) b(1:n)
Read (nin,*) x(1:n)
! Solve Ax = b using F11JEF
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call f11jef(method,precon,n,nnz,a,irow,icol,omega,b,tol,maxitn,x,rnorm, &
itn,work,lwork,iwork,ifail)
Write (nout,99999) 'Converged in', itn, ' iterations'
Write (nout,99998) 'Final residual norm =', rnorm
! Output x
Write (nout,99997) x(1:n)
99999 Format (1X,A,I10,A)
99998 Format (1X,A,1P,E16.3)
99997 Format (1X,1P,E16.4)
End Program f11jefe