/**
 * @file README_mod.txt
 *
 * @brief
 *
 * @copyright
 * Copyright (©) 2021 EPFL (Ecole Polytechnique Fédérale de Lausanne)
 * SPC (Swiss Plasma Center)
 *
 * SPClibs is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * SPClibs is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <https://www.gnu.org/licenses/>.
 *
 * @author
 * (in alphabetical order)
 * @author Trach-Minh Tran <trach-minh.tran@epfl.ch>
 */
1) Module parmg
   ============
  - types:
      grid2_type
       INTEGER, DIMENSION(2)    :: s, e, s0, e0, npt_loc, npt
       REAL(rkind), ALLOCATABLE :: x(:), y(:)
       TYPE(gvector_2d)         :: f, v
       TYPE(stencil_2d)         :: fdmat, restrict_mat

   - module procedures:
       creat_grid
       coarse (1d, 2d)
       exchange (gvector)
       prolong  (gvector)
       restrict (gvector)
       jacobi
       get_resids
       init_restrict (gvector)
       disp (0d, 1d array of int)
       get_lmax

   - Uses
       gvector
       stencil

2) Module stencil
   ==============
  - types:
        LOGICAL                  :: nluni
        INTEGER, DIMENSION(2)    :: ldim, gdim, s0, e0, s, e
        INTEGER                  :: npoints
        INTEGER, ALLOCATABLE     :: id(:,:)
        REAL(rkind), ALLOCATABLE :: val(:,:,:)

  - module procedures:
      init
      vmx
      laplacian
      putmat

  - operators:
      *: vmx

   - Uses
       gvector

3) Module gvector
   ==============
  - types:
      gvector_2d
        INTEGER, DIMENSION(2)    :: s, e ! vector internal bounds
        INTEGER, DIMENSION(2)    :: g    ! ghost cell widths
        REAL(rkind), ALLOCATABLE :: val(:,:)

  - module procedures:
      constructor (gvector_2d)
      disp
      norm2 (serial, mpi)
      
  - operators:
      + : add_scal, add_vec
      - : minus_vec, substract_vec
      * : scale_left, scale_right

  - assignment:
      = : from_scal, from_vec