Provided by: librheolef-dev_7.2-3build1_amd64 bug

NAME

       solver_option - direct and iterative solver options (rheolef-7.2)

DESCRIPTION

       This class implements a set of options for customizing a solver(4). An instance of this
       class can be supplied to the solver(4) constructor.

MAIN OPTION

       iterative

            This boolean flag controls the choice between an iterative or a direct method.
           Default is direct for matrix obtained from 1D or 2D PDE problems and iterative for 3D
           ones. The direct solver bases on the mumps library for a distributed environment and,
           otherwise, on the suitesparse or the eigen in a sequential one. The iterative solver
           bases on cg(5) conjugate gradient algorithm for symmetric positive definite matrix and
           on the gmres(5) algorithm otherwise.

OPTION FOR DIRECT SOLVERS

       preferred_library

            The direct solver bases on an external library: it could be either mumps, suitesparse
           or eigen. When all these libraries are available, then mumps is the default when is is
           well configured with either the scoth or the metis ordering library. When neither
           mumps nor suitesparse are available, the eigen choice is selected. This option allows
           one to impose an alternative choice e.g. suitesparse, by setting the string to
           'suitesparse'. This option can be provided as a list of choices, separated by a space
           or a coma, e.g. preferred_library='suitesparse eigen mumps'.

       default_preferred_library(a)

            This method returns all the the available libraries in the decreasing preference
           order. The result depends upon the matrix a, especially if it is symmetric definite
           positive or not, and whether it requires memory communications or not.

       used_library(a,sopt)

            This method returns the name of the available library that will be used by the solver
           when a direct solvers is selected. The result depends upon the properties of the a
           matrix and upon the solver option sopt, especially the sopt.preferred_library.

       compute_determinant

            Compute also the determinant of the matrix. Requires mumps or suitesparse.

       n_refinement

            Number of iterative refinement, when using a direct method (suitesparse only support
           it).

OPTION FOR ITERATIVE SOLVERS

       tol

            This floating parameter control the tolerance for the stopping criterion. Default is
           the machine epsilon for the default Float_2 type. Recall that the default Float_2 type
           is defined at Rheolef configuration time and is double by default, when no special
           configuration option is used.

       max_iter

            Maximum number of iteration when using an 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 relative 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 diststream(2) where residues are printed during iterations. When
           this pointer is zero, no errors are printed. Default is to print to derr standard
           diststream(2) error.

       label

            When printing errors, each line is prefixed by [label]. When the label is empty, each
           iterative algorithm uses its default label, e.g. 'cg' for the cg(5) conjugate
           gradient. By default the label is empty and this option is used to customize the
           convergence trace.

       krylov_dimension

            The dimension of the Krylov space used by the gmres(5) algorithm. Default is
           krylov_dimension=6.

OPTIONS FOR DEVELOPERS

       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

       This documentation has been generated from file linalg/lib/solver_option.h

       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        preferred_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           (1e3*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),
            preferred_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&);
         template <class T, class M>
         static std::string default_preferred_library (const csr<T,M>& a);
         template <class T, class M>
         static std::string used_library (const csr<T,M>& a, const solver_option& sopt = solver_option());

       };

AUTHOR

       Pierre  Saramito  <Pierre.Saramito@imag.fr>

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.