NAME

       solver_option - options for direct or interative solvers

DESCRIPTION

       This  class implements a set of options for direct or iterative solvers, as implemented by
       the solver(2). An instance of this class can be supplied to the solver constructor.

OPTIONS

       iterative
              Indicate if we want to use an iterative solver or  a  a  direct  one.   Default  is
              direct  for  1D  or  2D problems and iterative for 3D ones.  Direct solver is mumps
              when available, otherwise umfpack or builtin solver when none of these solvers  are
              available at Rheolef configure time.  Iterative solver is cg for symmetric positive
              definite systems and gmres otherwise.

OPTIONS FOR ITERATIVE SOLVERS

       tol    Tolerance for the stopping criterion.  Default  is  the  machine  epsilon  for  the
              default  Float type.  The default Float type is double defined at Rheolef configure
              time and is double by default, when no special configure option is used.

       max_iter
              Maximum number of iteration when using iterative method.

       absolute_stopping
              Absolute  or  relative  stopping  criterion.   With  the  absolute  criterion,  the
              algorithm  stops  when  norm(A*x-b)  <  tol,  otherwise it stops when norm(A*x-b) <
              tol*norm(b).  Default is to use an absolute stopping criterion.

       residue
              On return, gives the obtained residue, optionally divided by the initial  one  when
              using  a  relatiive  stopping.   It  is  less  or  equal  to tol when the iterative
              algorithm stops with succes.

       n_iter On return, gives the number of iterations performed.  It is always less or equal to
              max_iter when the iterative algorithm stops with succes.

       p_err  A  pointer  to  the  odiststeam  standard  error  where residues are printed during
              iterations.  When this pointer is zero, no errors are printed.  Default is to print
              to derr.

       label  When  printing  errors,  each line is prefixed by [@var{label]}.  When the label is
              empty, each iterative algorithm uses its default label, e.g. "cg" for the conjugate
              gradient cg.  By default the label is empty and this option is used to superset the
              algorithm default.

       krylov_dimension
              The dimension of the  Krylov  space  used  by  the  gmres  algorithm.   Default  is
              krylov_dimension=6.

OPTIONS FOR DIRECT SOLVERS

       n_refinement
              Number of iterative refinement, when using direct method (umfpack only support it).
              This option is only active when using iterative solvers.

       compute_determinant
              Compute also the determinant of the matrix.  This option is only active when  using
              direct solvers.  Requires mumps or umfpack.

       prefered_library
              When  both mumps and umfpack are available, then mumps is the default.  This option
              allows one to force to choose umfpack, by setting the string  to  "umfpack".   This
              option is only active when using direct solvers.

OPTIONS FOR DEVELOPPERS

       verbose_level
              Can be set to 0, 1, 2 or 3. The default is 0.

       level_of_fill
              Built an incomplete factorization with the prescribed level of fill [1:5].

       do_check
              Performs extra checks for debug.

       force_seq
              In  distributed  mode,  restrict the linear system resolution to diagonal blocs per
              process.  This option is only active when using the mumps direct solver.

       ooc    Out-of-core limit (Mo/percent depending on compilation options).  In development.

       amalgamation
              Level of amalgamation [10:70] for Kass.  In development.

IMPLEMENTATION

       class solver_option {
       public:
         typedef std::size_t size_type;
         static const long int  decide = -1;
         mutable long int   iterative;
         Float              tol;
         size_type          max_iter;
         bool               absolute_stopping;
         mutable Float      residue;
         mutable size_type  n_iter;
         odiststream*       p_err;
         mutable std::string label;
         size_type          krylov_dimension;
         size_type          n_refinement;
         bool               compute_determinant;
         std::string        prefered_library;
         size_type          verbose_level;
         bool               do_check;
         bool               force_seq;
         size_type          level_of_fill;
         size_type          amalgamation;
         size_type          ooc;

       // allocator and default values:

         solver_option()
          : iterative     (decide),
       #if defined(_RHEOLEF_HAVE_FLOAT128)
            tol           (1e6*std::numeric_limits<Float>::epsilon()),
       #else
            tol           (std::numeric_limits<Float>::epsilon()),
       #endif
            max_iter      (100000),
            absolute_stopping (true),
            residue       (0),
            n_iter        (0),
            p_err         (&derr),
            label         (),
            krylov_dimension (6),
            n_refinement  (2),
            compute_determinant(false),
            prefered_library(),
            verbose_level (0),
            do_check      (false),
            force_seq     (false),
            level_of_fill (1),
            amalgamation  (10),
            ooc           (20000)
         {
         }
         solver_option (const solver_option&);
         solver_option& operator= (const solver_option&);
       };

SEE ALSO

       solver(2)

COPYRIGHT

       Copyright (C) 2000-2018 Pierre Saramito <Pierre.Saramito@imag.fr> GPLv3+: GNU GPL  version
       3  or  later  <http://gnu.org/licenses/gpl.html>.   This is free software: you are free to
       change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.