c  Mahc_Evolve: Numerical Evolution of the General Relativistic Hydro Equations
c  Copyright (C) 2001 Mark Miller

/*@@
  @file      Mahc_corr_apply_update.F
  @date      December 1999
  @author     Mark Miller
  @desc
     Apply the hydro update for the corrector step.
  @enddesc
@@*/

#include "cctk.h"
#include "cctk_Parameters.h"
#include "cctk_Arguments.h"


/*@@
  @routine    Mahc_corr_apply_update
  @date       December 1999
  @author     Mark Miller
  @desc
     Apply the hydro update for the corrector step.
  @enddesc
  @calls
  @calledby
  @history
  @endhistory
@@*/

      subroutine Mahc_corr_apply_update(CCTK_FARGUMENTS)
      implicit none
      DECLARE_CCTK_FARGUMENTS
      DECLARE_CCTK_PARAMETERS

      integer order,CCTK_Equals
      CCTK_REAL frac

      order = -1
      if (CCTK_EQUALS(hydro_order,'fluxlim')) then
         order = 2
      endif
      if (CCTK_EQUALS(hydro_order,'upwind')) then
         order = 1
      endif 
c     if we only want 1st order, then we are done!
      if(order .lt. 2) then
         return
      endif

      frac = 1.0d0
      call apply_del_hydro(CCTK_FARGUMENTS,frac)

c     if we got this far, we must be second order:
      dens = 0.5d0 * (dens + dens_p)
      sx = 0.5d0 * (sx + sx_p)
      sy = 0.5d0 * (sy + sy_p)
      sz = 0.5d0 * (sz + sz_p)
      tau = 0.5d0 * (tau + tau_p)

c      call CCTK_SyncGroup(cctkGH,"gen_rel_perfect_fluid::Mahc_evol_vars")


      return
      end