#$
#$=head1 NAME
#$
#$cgmeth  - conjugate gradient method
#$
#$=head1 SYNOPSIS
#$
#$C<call cgtest( x, yy, rr, fff, niter)>
#$
#$=head1 INPUT PARAMETERS
#$
#$=over 4
#$
#$=item yy   - C<real(:)>  
#$
#$=item rr   - C<real(:)>  
#$
#$=item fff  - C<real(:)>  
#$
#$=back
#$
#$=head1 OUTPUT PARAMETERS
#$
#$=over 4
#$
#$=item x  - C<real(:)>  
#$
#$=back
#$
#$=head1 DESCRIPTION
#$
#$ setup of conjugate gradient descent, minimize  SUM rr(i)**2
#$             nx
#$ rr(i)  =   sum fff(i,j) * x(j)  -  yy(i)
#$            j=1
#$
#$
#$=head1 SEE ALSO
#$
#$L<matmult>, L<cgstep>,L<solver>
#$
#$=head1 LIBRARY
#$
#$B<geef90>
#$
#$=cut
#$
module cgmeth {
  use matmult
  use cgstep_mod
  use simple_solver
contains
  # setup of conjugate gradient descent, minimize  SUM rr(i)**2
  #             nx
  # rr(i)  =   sum fff(i,j) * x(j)  -  yy(i) 
  #            j=1
  subroutine cgtest( x, yy, rr, fff, niter) {
    real, dimension (:), intent (out) :: x, rr
    real, dimension (:), intent (in)  :: yy
    real, dimension (:,:), pointer    :: fff
    integer,             intent (in)  :: niter

    call matmult_init( fff)

    call solver( matmult_lop, cgstep, x, yy, niter, res = rr)

    call cgstep_close ()
  }
}