source: trunk/NEMO/OPA_SRC/SOL/solver.F90 @ 3

MODULE solver
   !!======================================================================
   !!                     ***  MODULE  solver  ***
   !! Ocean solver :  initialization of ocean solver
   !!=====================================================================

   !!----------------------------------------------------------------------
   !!   solver_init: solver initialization
   !!----------------------------------------------------------------------
   !! * Modules used
   USE oce             ! ocean dynamics and tracers variables
   USE dom_oce         ! ocean space and time domain variables 
   USE zdf_oce         ! ocean vertical physics variables
   USE sol_oce         ! solver variables
   USE solmat          ! ???
   USE solisl          ! ???
   USE obc_oce         ! Lateral open boundary condition
   USE in_out_manager  ! I/O manager
   USE lbclnk          ! ocean lateral boundary conditions (or mpp link)

   IMPLICIT NONE

   !!----------------------------------------------------------------------
   !!   OPA 9.0 , LODYC-IPSL  (2003)
   !!----------------------------------------------------------------------

CONTAINS

   SUBROUTINE solver_init
      !!----------------------------------------------------------------------
      !!                  ***  ROUTINE solver_init  ***
      !!                   
      !! ** Purpose :   Initialization for the solver of the elliptic equation:
      !!       * default option: barotropic stream function system
      !!         and islands initialization (if l_isl=T)
      !!       * key_dynspg_fsc = T : transport divergence system. No specific
      !!         treatment of islands.
      !!      
      !! ** Method :
      !!       - Compute the local depth of the water column at u- and v-point
      !!      (key_dynspg_fsc = T) or its inverse (key_dynspg_rl = T).
      !!      The local depth of the water column is computed by summing 
      !!      the vertical scale factors. For its inverse, the thickness of
      !!      the first model level is imposed as lower bound. The inverse of
      !!      this depth is THEN taken and masked, so that the inverse of the
      !!      local depth is zero when the local depth is zero.
      !!       - Construct the matrix of the elliptic system by a call to
      !!      solmat.F routine.
      !!       - island (if l_isl=T)
      !!            isl_dom: find islands from the bathymetry file
      !!            isl_bsf: compute the island barotropic stream function
      !!            isl_mat: compute the inverse island matrix
      !!            set mbathy to the number of non-zero w-levels of a water
      !!            column (the minimum value of mbathy is 2):
      !!                  mbathy = min( mbathy, 1 ) + 1
      !!
      !! ** Action : - hur, hvr : masked inverse of the local depth at
      !!                                u- and v-point. (key_dynspg_rl = T)
      !!             - hu, hv   : masked local depth at u- and v- points
      !!                                (key_dynspg_fsc = T)
      !! References :
      !!      Jensen, 1986: adv. phys. oceanogr. num. mod.,ed. o brien,87-110.
      !!      Madec & Marti, 1990: internal rep. LODYC, 90/03., 29pp.
      !!
      !! History :
      !!        !  90-10  (G. Madec)  Original code           
      !!        !  93-02  (O. Marti)                         
      !!        !  97-02  (G. Madec)  local depth inverse computation
      !!        !  98-10  (G. Roullet, G. Madec)  free surface 
      !!   9.0  !  03-07  (G. Madec)  free form, F90
      !!----------------------------------------------------------------------
      !! * Local declarations
      INTEGER :: ji, jj   ! dummy loop indices

      NAMELIST/namsol/ nsolv, nmax, eps, sor, epsisl, nmisl, rnu
      !!----------------------------------------------------------------------

      IF(lwp) WRITE(numout,*)
      IF(lwp) WRITE(numout,*) 'ini_sol : solver to compute the surface pressure gradient'
      IF(lwp) WRITE(numout,*) '~~~~~~~'

      ! open elliptic solver statistics file
      CALL ctlopn( numsol, 'solver.stat', 'UNKNOWN', 'FORMATTED', 'SEQUENTIAL',   &
                   1, numout, lwp, 1 )


      ! 0. Define the solver parameters
      !    ----------------------------
      ! Namelist namsol : elliptic solver / islands / free surface
      REWIND( numnam )
      READ  ( numnam, namsol )

#if defined key_feti
      ! FETI algorithm, we force nsolv at 3
      nsolv = 3
#endif


      ! 0. Parameter control and print
      !    ---------------------------

      ! Control print
      IF(lwp) WRITE(numout,*) '          Namelist namsol : set solver parameters'

      IF(lwp) THEN
         WRITE(numout,*)
         WRITE(numout,*) '             type of elliptic solver        nsolv  = ', nsolv
         WRITE(numout,*) '             maximum iterations for solver  nmax   = ', nmax
         WRITE(numout,*) '             absolute precision of solver   eps    = ', eps
         WRITE(numout,*) '             optimal coefficient of sor     sor    = ', sor
         IF(l_isl) WRITE(numout,*) '             absolute precision stream fct  epsisl = ', epsisl
         IF(l_isl) WRITE(numout,*) '             maximum pcg iterations island  nmisl  = ', nmisl
         WRITE(numout,*) '             free surface parameter         rnu    = ', rnu
         WRITE(numout,*)
      ENDIF

#if defined key_dynspg_fsc 
         IF(lwp) WRITE(numout,*)
         IF(lwp) WRITE(numout,*) '          *** free surface formulation'
         IF( l_isl ) THEN
            IF(lwp) WRITE(numout,cform_err)
            IF(lwp) WRITE(numout,*) ' key_islands inconsistent with key_dynspg_fsc'
            nstop = nstop + 1
         ENDIF
#endif
#if defined key_dynspg_rl
         IF(lwp) WRITE(numout,*)
         IF(lwp) WRITE(numout,*) '          *** Rigid lid formulation'
#endif
#if defined key_dynspg_fsc && defined key_dynspg_rl
         IF(lwp) WRITE(numout,cform_err)
         IF(lwp) WRITE(numout,*) '          Chose between free surface or rigid-lid, not both'
         nstop = nstop + 1
#endif

      SELECT CASE ( nsolv )

      CASE ( 1 )                ! preconditioned conjugate gradient solver
         IF(lwp) WRITE(numout,*) '          use a preconditioned conjugate gradient solver'

      CASE ( 2 )                ! successive-over-relaxation solver
         IF(lwp) WRITE(numout,*) '          use a successive-over-relaxation solver'

      CASE ( 3 )                ! FETI solver
         IF(lwp) WRITE(numout,*) '          use the FETI solver'
#if ! defined key_mpp
         IF(lwp) WRITE(numout,*) ' The FETI algorithm is used only with the key_mpp option'
         nstop = nstop + 1
#else
         IF( jpnij == 1 ) THEN
            IF(lwp) WRITE(numout,*) ' The FETI algorithm needs more than one processor'
            nstop = nstop + 1
         ENDIF
#endif
         
      CASE DEFAULT
         IF(lwp) WRITE(numout,cform_err)
         IF(lwp) WRITE(numout,*) '          bad flag value for nsolv = ', nsolv
         nstop = nstop + 1
         
      END SELECT


      ! Construction of the elliptic system matrix
      ! ------------------------------------------

      CALL sol_mat


      IF( l_isl ) THEN
      
         ! Islands in the domain
         ! ---------------------

         IF ( jpisl == 0 ) THEN
             IF(lwp)WRITE(numout,cform_err)
             IF(lwp)WRITE(numout,*) ' bad islands parameter jpisl =', jpisl
             nstop = nstop + 1
         ENDIF

         ! open Island streamfunction statistic file
         CALL ctlopn( numisp, 'islands.stat', 'UNKNOWN', 'FORMATTED', 'SEQUENTIAL',   &
            &         1     , numout        , lwp      , 1                         )
   
         CALL isl_dom       ! Island identification

         CALL isl_bsf       ! Island barotropic stream function

         CALL isl_mat       ! Comput and invert the island matrix

         ! mbathy set to the number of w-level (minimum value 2)
         DO jj = 1, jpj
            DO ji = 1, jpi
               mbathy(ji,jj) = MAX( 1, mbathy(ji,jj) ) + 1
            END DO
         END DO

      ENDIF

   END SUBROUTINE solver_init

   !!======================================================================
END MODULE solver