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    !------------------------------------------------------------------------------|
    !------------------------------------------------------------------------------|
    !                                                                              |
    !              ||===\\                                                         |
    !              ||    \\                                                        |
    !              ||     ||   //==\\   ||  ||   //==||  ||/==\\                   |
    !              ||     ||  ||    ||  ||  ||  ||   ||  ||    ||                  |
    !              ||    //   ||    ||  ||  ||  ||   ||  ||                        |
    !              ||===//     \\==//    \\==\\  \\==\\  ||                        |
    !                                                                              |
    !              Input File                                                      |
    !------------------------------------------------------------------------------|
    !------------------------------------------------------------------------------|
    
    This file is read by two subroutines in the code:
    - read_controlling_parameters
    - read_input_file
    The indications between [] indicate the type of the read parameter. It can be
    an integer [int], a real*8 [dp], a character chain [char] or a boolean [bool].
    
    
    CONTROLLING PARAMETERS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]debug is a parameter that switches on/off various prints and outputs
    (the level of printing for error, warning and messages of the solver id%cntl(4)
    is set to the debug value).
    if debug is zero, no debugging 
    if debug is equal to one, this triggers the terminal display of some key
    parameters 
    if debug is equal to two, same as debug equal to one, and the code produces
    various vtk files in the DEBUG subdirectories (surfaces, olsf, ...), as well as
    cross sections for all nonlinear iterations. Careful, memory consuming!
    
          debug = 1
    
    [bool]doDoRuRe is a flag that triggers the production of output files needed to
    produce the DoRuRes. DoRuRe stands for 'Douar Run Report'. 
    
           doDoRuRe = F
    
    [bool]compute_qp_gram triggers the production of qpgrams for every grid.
    
          compute_qpgram = F
    
    [bool]compute_reaction_forces toggles on/off the reaction forces computations.
    
          compute_reaction_forces = F
    
    
    RESTART
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]irestart is a restart flag; if irestart is not 0, the run will restart from
    an output file given by [char]restartfile and at step.
    
          irestart=0
    
          restartfile=OUT/time_0000.bin
    
    
    TIMESTEPPING
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [dp]dt is the time step length (if dt is negative, courant conidition is used
    and automatic time stepping is turned on)
    
          dt=1.07d-1
    
    [int]nstep is the number of time steps
    
          nstep = 50
    
    [dp]courant is only used when dt is negative; it determines the size of the time
    step from the maximum value of the velocity field amplitude. The time step s
    the product of courant by the ratio of the smallest leaf size by the maximum
    velocity.
    
          courant=.5d0
    
    [bool]normaladvect is a flag used to determine which algorithm to use to
    calculate the new geoletry of the normals to the surfaces at the nodes on the
    surfaces
    if normaladvect is T, the normals are advected using the velocity gradient
    if normaladvect is F, the normals are re-computed from the geometry of the
    surface
    
          normaladvect = T
    
    
    GRID ITERATIONS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]griditer is a flag that allows for nonlinear iterations; when positive, a
    fixed number (griditer) of iterations is permitted; when negative, the number of
    nonlinear iterations is determined by a convergence criterion.
    
          griditer = -100
    
    [dp]octree_refine_ratio is the threshold value used to determine whether the
    octree has converged or not. the larger the value, the less stringent the test.
    
          octree_refine_ratio=.025d0
    
    
    NONLINEAR ITERATIONS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]nonlinear_iterations is the maximum number of nonlinear iterations (i.e.
    the iterations on a given constant grid)
    if nonlinear_iterations is positive, it simply is the number of nonlinear
    iterations performed for each grid. When negative it indicates an upper bound
    of nonlinear iterations, but the actual number of nonlinear iterations is
    determined by a convergence criterion (see the 'tol' parameter)
    
          nonlinear_iterations = 30 
    
    [dp]tol is the relative tolerance used to estimate convergence on the computed
    velocity field
    
          tol=0.01d0
    
    [bool]adaptive_tol is a flag that toggles on/off the evolution of the tol
    parameter with the grid level: when velocity convergence is reached on a grid,
    the latest meaure of the velocity difference between the two last obtained
    solutions is put in tol, so that on the following generated grid, the solution
    reaches at least the same level of convergence. It allows to start with a not
    too stringent value of tol at uniform octree level that evolves with every
    grid, assuming that increasing the level of refinement of the octree allows to
    better capture the solution, hence allowing a tighter convergence. 
    
          adaptive_tol = F
    
    
    OCTREES
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]leveluniform_oct is the level of uniform discretization of space; note that
    a level is a power of two used to divide the unit cube
    
          leveluniform_oct = 6
    
    [int]levelmax_oct is maximum level of octree discretization
    
          levelmax_oct = 7
    
    [double]vex is the vertical exaggeration scaling factor that allows for
    variable aspect ratio elements. The value should range between 0-1, which
    will be multiplied by the vertical scale of the model domain. For example, a
    value of 0.25 would correspond to a model of dimensions 1x1x0.25, where the
    elements are 1/4 as tall as they are wide.
    
          vex = 0.2d0
    
    [bool]ismooth is a flag to impose an additional level of smoothing after
    refinement for the surfaces and strain rate. It ensures that no leaf is flanked
    by other leaves differing by more than 1 level of refinement
    
          ismooth = F
    
    [int]noctreemax is the maximum size of any octree used in all computations
    
          noctreemax=10000000
    
    [dp]refine_ratio is used to determine octree refinement based on a given
    criterion. All leaves where the criterion is larger than refine_ratio times the
    maximum of this criterion are refined 
    
          refine_ratio=-5500
    
    [int]refine_criterion determines which refinement algorithm is to be used.
    Several criteria exist for the refinement of the osolve octree. 1 is the second 
    invariant of the deviatoric strain-rate tensor; 2 is the sum of the squares of
    the diagonal terms of the deviatoric strain-rate tensor; 3 is the second
    invariant of the deviatoric strain rate tensor timses the leaf size. any other
    value sets the criterion to zero and leads to no refinement. 
    
          refine_criterion=0
    
    [int]initial_refine_level is the initial level at which the refinement of the
    octree will be performed. it has to be smaller than levelmax_oct
    this should be used (different from levelmax_oct) in case the flow is very 
    localized (nonlinear/plastic analysis)
    
          initial_refine_level = 7
    
    [bool]renumber_nodes is a flag that can toggle on/off the renumbering of the
    nodes by mean of Sloan's algorithm (T/F)
    
          renumber_nodes = T
    
    
    PRESSURE
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]smoothing_type is a parameter allows to choose which type of smoothing is
    to be applied to the pressure field: 0 is none, 1 is center->nodes->center, 2 is
    the same, but weighted by neighbouring elemental volumes, 3 is regular grid+SPH,
    and 4 is SPH.  
    
          smoothing_type = 1
    
    
    CLOUD
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]npmin and [int]npmax are used to update the 3D volumetric cloud. npmin
    corresponds to the minimum number of particles in any leaf; npmax is the maximum
    allowable number in any leaf
    
          npmin=1
          npmax=4
    
    
    FEM + DIVFEM + MUMPS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]matrule determines the rule used to assign material properties to
    elements that are cut by a surface. The default value (0) will use divFEM to
    determine the element properties. A value of 1 will assign the properties of
    the material that occupies the majority of the element, whereas a value of 2
    will assign the properties of the volumetric minority of the element. NOTE:
    divFEM is always used for any element containing void material.
    
          matrule=1
    
    [int]levelcut is the number of levels used to estimate the volume integrals in
    the divFEM algorithmi for cut cells; by testing, it has been estimated that a
    value of 2 is very accurate
    
          levelcut=2
    
    [int]levelapprox is the number of levels used to estimate the remaining
    integrals using an improved version of Marthijn's clever algorithm, usually 3 is
    plenty
    
          levelapprox=3
    
    [dp]penalty is a global penalty parameter used to impose the bad faces or
    incompatible faces linear constraints
    
          penalty=1.d8
    
    [bool]excl_vol is a parameter that toggles off the assumption that lsf's are
    built on top of one another
    
          excl_vol = F 
    
    
    TEMPERATURE
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [dp] ztemp is the height interval between which a linear temperature gradient is
    set: the temperature is 1 at the bottom, and 0 at ztemp.
    [dp] tempscale
    
          calculate_temp = F
    
          ztemp = .026564d0
    
          tempscale=100.d0
    
    
    ISOSTASY
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
          isostasy = F
    
          flexure = F
    
          isobc = F
    
    MATERIALS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]nmat is number of materials
    
          nmat=2
    
    [int]material0 determines what is the material above the 1st surface (the free
    surface) if material0 is 0 then it is the void and the properties "0" are used
    for that part of the model; otherwise the material is one of the material,
    comprised between 1 and nmat
    
          material0 = 0
    
    [bool]bulkvisc determines whether the user will input a material penalty value
    that scales with the shear viscosity or whether an independent bulk viscosity
    will be listed. If true, the values listed for [dp]penaltyi below should be
    bulk viscosity values for each material. Otherwise, the listed penalty value
    will be multiplied by the shear viscosity to enforce the incompressibility
    condition.
    
          bulkvisc = F
    
    [bool]init_e2d determines whether an initial e2d value will be used to put
    plastic materials on yield in the first time step, or whether the standard
    initial material viscosity will be used. If true, an initial e2d value will be
    used to ensure plastic materials behave as desired.
    
          init_e2d = T
    
    [dp]e2d0 is the initial strain rate value to use if init_e2d is true. This
    value will be used in only the first nonlinear iteration of the first time
    step and should be in scaled DOUAR units.
    
          e2d0 = 5.d-4
    
    [dp]densityi, [dp]viscosityi and [dp]penaltyi are the density, viscosity and
    incompressibility used for material i; there should be nmat sets of material
    properties; there should also be a nil material if material0 has been set to 0
    [dp]expon is the nonlinear viscosity exponent
    [dp]diffusivity is the heat diffusivity
    [dp]heat is the heat production
    
    [char]plasticity_type is the type of plasticity
    - No    -> no plasticity, purely (nonlinear) viscous material
    - vM    -> von Mises yield criterion
            -> [dp]plasticity_1st_param is the yield strength
    - DPI-IV-> Drucker-Prager type of yield criterion
      DPI   -> the yield locus passes through the inner apices of the Mohr-Coulomb
               hexagon
      DPII  -> the yield locus passes through the outer apices of the Mohr-Coulomb
               hexagon
      DPIII -> The average case, intermediate to DPI and DPII
      DPIV  -> Plane strain Drucker-Prager formulation
            -> [dp]plasticity_1st_param is the angle phi
            -> [dp]plasticity_2nd_param is the cohesion c
            -> [dp]plasticity_3rd_param is the accumulated strain minimum, beyond
               which phi is modified
            -> [dp]plasticity_4th_param is the accumulated strain maximum, beyond
               which phi is set to the value in plasticity_5th_param
            -> [dp]plasticity_5th_param is the final phi value, if modified
    - DPV   -> Drucker-Prager type of yield criterion that does not calculate the
               values of alpha and k from phi and c. They are specified here. Note
               that strain softening cannot be used for this DP type.
            -> [dp]plasticity_1st_param is alpha
            -> [dp]plasticity_2nd_param is k
    - DPVI  -> Drucker-Prager type of yield criterion that uses the equation below
               sigma_y = pressure * tan(phi) + c
            -> [dp]plasticity_1st_param is the angle phi
            -> [dp]plasticity_2nd_param is the cohesion c
            -> [dp]plasticity_3rd_param is the accumulated strain minimum, beyond
               which phi is modified
            -> [dp]plasticity_4th_param is the accumulated strain maximum, beyond
               which phi is set to the value in plasticity_5th_param
            -> [dp]plasticity_5th_param is the final phi value, if modified
    - DPVII -> Drucker-Prager type of yield criterion that uses the same 2D
               formulation that is used in Sopale
               (sigma_y = pressure*sin(phi) + c*cos(phi))
            -> [dp]plasticity_1st_param is the angle phi
            -> [dp]plasticity_2nd_param is the cohesion c
            -> [dp]plasticity_3rd_param is the accumulated strain minimum, beyond
               which phi is modified
            -> [dp]plasticity_4th_param is the accumulated strain maximum, beyond
               which phi is set to the value in plasticity_5th_param
            -> [dp]plasticity_5th_param is the final phi value, if modified
    - MC    -> Mohr-Coulomb type of yield criterion
            -> [dp]plasticity_1st_param is the angle phi
            -> [dp]plasticity_2nd_param is the cohesion c
            -> [dp]plasticity_3rd_param is the accumulated strain minimum, beyond
               which phi is modified
            -> [dp]plasticity_4th_param is the accumulated strain maximum, beyond
               which phi is set to the value in plasticity_5th_param
            -> [dp]plasticity_5th_param is the final phi value, if modified
    
          density0              = 0.d0
          viscosity0            = 1.d-5
          penalty0              = 1.d8
          expon0                = 1.d0
          diffusivity0          = 1.d0
          heat0                 = 0.d0
          activationenergy0     = 0.d0
          plasticity_type0      = No
    
          density1              = -1.d0
          viscosity1            = 1.d5
          penalty1              = 1.d8
          expon1                = 1.d0
          diffusivity1          = 5.98d-4
          heat1                 = 0.d0
          activationenergy1     = 0.d0
          plasticity_type1      = DPVII
          plasticity_1st_param1 = 20.d0
          plasticity_2nd_param1 = 0.d0
          plasticity_3rd_param1 = 0.5d0
          plasticity_4th_param1 = 1.5d0
          plasticity_5th_param1 = 20.d0
          
          density2              = -.935d0
          viscosity2            = 1.d-3
          penalty2              = 1.d8
          expon2                = 1.d0
          diffusivity2          = 1.20d-3
          heat2                 = 0.d0
          activationenergy2     = 0.d0
          plasticity_type2      = No
    
    [dp]viscositymin and viscositymax are bounds on the viscosity (if negative bound
    is not imposed) These bounds are introduced to prevent the viscosity to reach
    unrealistic values, especially when using non-linear (power-law or brittle)
    rheologies
    
          viscositymin=1.d-4
          viscositymax=1.d7
    
    
    SURFACES
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]ns is number of surfaces to track
    
          ns=2
    
    for each surface, one needs to define a levelt, itype, material, surface_type,
    activation_time and surface_params.
    - [int]levelt is the inital level for the particles on the surface; to be
      accurate and avoid holes in the surface during definition of the lsf, one
      should use levelt eq to levelmax_oct+1 for all surfaces as a minimum value; 
    - [int]itype should be 1 for foldable surfaces or 0 for nonfoldable surfaces; 
    - [int]material is the material type refering to the table of material available
      (max nmat);
    - [dp]activation_time is the time the surface becomes active (before that time,
      it is glued to the 0th surface). this parameter is useful when defining
      stratigraphic horizons; default is -1, ie the surface is not glued to the free
      surface
    - [int]surface_type is comprised between 1 and 8. 
      1 corresponds to  a flat surface, 
        -> surface_param_01 is the z level
      2 to a rectangular emboss, 
        -> surface_param_01 is the z level
        -> surface_param_02 and 03 are x1,x2 
        -> surface_param_04 and 05 are y1,y2 
        -> surface_param_06 is the thickness 
      3 to a convex spherical emboss, 
        -> surface_param_01 is the z level
        -> surface_param_02 and 03 are x0,y0 
        -> surface_param_04 is the radius 
      4 to concave spherical emboss,
        -> surface_param_01 is the z level
        -> surface_param_02 and 03 are x0,y0 
        -> surface_param_04 is the radius 
      5 to a double rectangular emboss, 
        -> surface_param_01 is the z level
        -> surface_param_02 and 03 are x1,x2 
        -> surface_param_04 and 05 are x3,x4 
        -> surface_param_06 and 07 are y1,y2 
        -> surface_param_08 and 09 are y3,y4 
        -> surface_param_10 is the thickness 
      6 to a sinus, 
        -> surface_param_01 is the z level
        -> surface_param_02 is the wavelength 
        -> surface_param_03 is the amplitude 
      7 to a noisy surface, 
        -> surface_param_01 is the z level
        -> surface_param_02 is the noise amplitude
      8 to a double sinus.
        -> surface_param_01 is the z level
        -> surface_param_02 is the x-wavelength 
        -> surface_param_03 is the x-amplitude 
        -> surface_param_04 is the y-wavelength 
        -> surface_param_05 is the y-amplitude
      12 for a rectangular emboss with defined margin slope 
        -> surface_param_01 is the z level
        -> surface_param_02 and 03 are x1,x2 
        -> surface_param_04 and 05 are y1,y2 
        -> surface_param_06 is the thickness 
        -> surface_param_07 is the slope in degrees
        - [int]leveloct is the level at which the octree will be refined in the vicinity
      of the surface.
    
          levelt1             = 8
          itype1              = 0
          surface_type_1      = 12
          rand1               = F
          surface_param_01_1  = 0.01289d0
          surface_param_02_1  = -0.5d0
          surface_param_03_1  = 0.5d0
          surface_param_04_1  = -1.d0
          surface_param_05_1  = 2.d0
          surface_param_06_1  = -0.01289d0
          surface_param_07_1  = 1.47676d0
          material1           = 1
          activation_time_1   = -1. 
          leveloct1           = 7
          stretch1            = 1.5d0
          anglemax1           = 180.d0
          criterion1          = 1
          anglemaxoctree1     = 180.d0
          spread_surface_points1 = 1
    
          levelt2             = 8
          itype2              = 0
          surface_type_2      = 12
          rand2               = F
          surface_param_01_2  = 0.d0
          surface_param_02_2  = 0.0625d0
          surface_param_03_2  = 0.9375d0
          surface_param_04_2  = -1.d0
          surface_param_05_2  = 2.d0
          surface_param_06_2  = -0.01289d0
          surface_param_07_2  = 87.5d0
          material2           = 2
          activation_time_2   = -1.
          leveloct2           = 7
          stretch2            = 1.5d0
          anglemax2           = 180.d0
          criterion2          = 1
          anglemaxoctree2     = 180.d0
          spread_surface_points2 = 0
    
    [int]niter_move is the number of iterations used to update particle positions
    using an implicit, mid-point algorithm (default is 10)
    
          niter_move = 10
    
    [dp]stretch is the maximum allowed increase in linear length between two
    initially adjacent particles on any surface; when this stretch is achieved, a
    new particle is inserted on the surface, half-way along the stretched edge
    
          stretch = 1.5d0
    
    [dp]anglemax is the maximum allowed angle between two adjacent normals
    when the angle is reached a new point is inserted beteen the two points to
    reduce the angle between the two normals
    
          anglemax=180.d0
    
    [int]criterion is criterion used to define the octree in the vicinity of the
    sufaces; criterion 1 corresponds to imposing that all leaves that are cut by any
    of the surfaces must be at level levelmax_oct; criterion 2 corresponds to
    imposing that discretization is proportional to the curvature of the surface;
    curvature is calculated from the local divergence of the normals. criterion 3
    corresponds to imposing that all leaves that contain at least one particle of
    any surface is at levelmax_oct; 
    
          criterion = 2
    
    [dp]anglemaxoctree is only defined for criterion 2; t is the maximum allowable
    angle between two adjacent normals; if the angle is greater than anglemaxoctree,
    the local octree leaves are forced to be at level levelmax_oct; otherwise they
    are proportionally larger (smaller levels) (default is 10)
    
         anglemaxoctree = 10.d0
    
    
    REFINEMENT IN BOXES
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]nboxes is the number of boxes in which the user imposes a set level of
    discretization
    
          nboxes = 1
    
    for each box we need to specify the two end corners and the level
    the syntax is [dp]boxnx0, [dp]boxnx1, [dp]boxny0, [dp]boxny1, [dp]boxnz0,
    [dp]boxnz1 and boxnlevel where n is the box number
    
          box1x0=0.d0
          box1x1=1.d0
          box1y0=0.d0
          box1y1=1.d0
          box1z0=0.d0
          box1z1=.03d0
          box1level=7
    
          box2x0=0.d0
          box2x1=.75d0
          box2y0=.4d0 
          box2y1=.6d0
          box2z0=.05d0
          box2z1=.25d0
          box2level=7
    
          box3x0=0.d0
          box3x1=1.d0
          box3y0=0.d0
          box3y1=1.d0
          box3z0=0.d0
          box3z1=.001d0
          box3level=6
    
          box4x0=.4875d0
          box4x1=.5125d0
          box4y0=.4875d0
          box4y1=.5125d0
          box4z0=.0d0
          box4z1=1.d0
          box4level=9
    
    
    REFINEMENT ON CUBE FACES
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    [bool]ref_on_faces toggles on/off the user imposed refinement on faces.
    For each of the six faces of the cube, on defines the level at which the
    desired area is to be refined. this area is given by bottom, top, left and
    right coordinates that are comprised between 0 and 1
    faces 1,2,3,4,5,6 respectively correspond to x=0,x=1,y=0,y=1,z=0,z=1
    
          ref_on_faces = F
    
          level_face1=5
          b1=.02
          t1=.51
          l1=.11
          r1=.81
          level_face2=5
          b2=.45
          t2=.55
          l2=.46
          r2=.56
          level_face3=5
          b3=.0
          t3=.2
          l3=.3
          r3=.7
          level_face4=5
          b4=.4
          t4=.5
          l4=.14
          r4=.4
          level_face5=6
          b5=0.
          t5=1.
          l5=0.
          r5=0.75
          level_face6=5
          b6=.26
          t6=.56
          l6=.16
          r6=.86
    
    
    EROSION
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [bool]erosion is a flag that toggles on/off the erosion. 
    
          erosion = F
    
    if erosion is on, one also needs to set the erosion level/height, [dp]zerosion
    Note that this is a first attempt at erosion; in future versions, DOUAR
    should be easily linked to a surface processes model like CASCADE
    
          zerosion=.0428d0
    
    If erosion is on, one also needs to define a length scale and a velocity scale
    to properly translate the uplift rate produced by DOUAR into something that is
    adequate for CASCADE; 
    [dp]length_scale is the scale of the unit model in km 
    [dp]velocity_scale is the velocity scale in km/Myr. 
    if length_scale is negative, erosion is assumed to be perfect (no call to
    CASCADE is needed)
    
          length_scale=-600.d0
          velocity_scale=50.d0
    
    One then needs to define the erosion constants in CASCADE
    [dp]fluvial_erosion is the fluvial erosion constant in 1/m^2
    [dp]diffusion_erosion is the diffusion erosion constant in m^2/yr
    (4d-2 32d-2)
    
          fluvial_erosion=4.d-2
          diffusion_erosion=32.d-2
    
    One finally needs to specify the boundary conditions for CASCADE
    if [int]baselevelx0 is set to 1 then the boundary at x=0 is set at baselevel
    (water and sediment exit)
    if [int]baselevelx1 is set to 1 then the boundary at x=1 is set at baselevel
    (water and sediment exit)
    if [int]baselevely0 is set to 1 then the boundary at y=0 is set at baselevel
    (water and sediment exit)
    if [int]baselevely1 is set to 1 then the boundary at y=1 is set at baselevel
    (water and sediment exit)
    
          baselevelx0=1
          baselevelx1=1
          baselevely0=0
          baselevely1=1
    
    
    MATRIX VISUALISATION
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [bool]visualise_matrix allows the user to turn on the visual representation of
    the matrices used in the code. Be careful, the generated postscript files are
    huge!
    
          visualise_matrix = F
    
    
    CROSS SECTIONS
    _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
    
    [int]nsections is the number of cross-sections to be output. [dp]scale is the
    scale used to produce the postscript file.
    [int]xyz takes values 1, 2 or 3, and corresponds to planes defined by
    x=constant, y=constant, and z=constant resp.
    The [bool]flags are self explanatory. [char]colormap is the chosen colormap (jet
    or hot). [int]ncolours is the number of colours used to produce the plot. 
    
    nsections = 0
    
    xyz_1          = 1 
    slice_1        = 0.5001
    flag_press_1   = T
    flag_spress_1  = T 
    flag_e2d_1     = T
    flag_e3d_1     = F
    flag_lode_1    = F 
    flag_crit_1    = F 
    flag_grid_1    = T 
    flag_mu_1      = F   
    flag_u_1       = F
    flag_v_1       = F
    flag_w_1       = F
    flag_q_1       = F 
    flag_uvw_1     = F 
    flag_lsf_1     = F 
    flag_vfield_1  = F 
    flag_colour_1  = T
    flag_plastic_1 = F
    flag_velvect_1 = T
    scale_1        = 500.
    colormap_1     = jet
    ncolours_1     = 256
    
    xyz_2          = 2
    slice_2        = 0.901
    flag_press_2   = T
    flag_e2d_2     = T
    flag_e3d_2     = F 
    flag_lode_2    = F 
    flag_crit_2    = F 
    flag_grid_2    = F 
    flag_mu_2      = F   
    flag_u_2       = F
    flag_v_2       = F
    flag_w_2       = F
    flag_q_2       = F 
    flag_uvw_2     = F 
    flag_lsf_2     = F 
    flag_vfield_2  = F 
    flag_colour_2  = T
    flag_plastic_2 = F
    flag_velvect_2 = F
    scale_2        = 800.
    colormap_2     = jet 
    ncolours_2     = 256
    
    
    xyz_3          = 3
    slice_3        = 0.0010
    flag_press_3   = F 
    flag_e2d_3     = F
    flag_e3d_3     = F
    flag_lode_3    = F 
    flag_crit_3    = F 
    flag_grid_3    = F 
    flag_mu_3      = F   
    flag_u_3       = F
    flag_v_3       = F
    flag_w_3       = F
    flag_q_3       = F
    flag_uvw_3     = F 
    flag_lsf_3     = F 
    flag_vfield_3  = F 
    flag_colour_3  = T
    flag_plastic_3 = F
    flag_velvect_3 = F
    scale_3        = 400.
    colormap_3     = jet
    ncolours_3     = 256