solver_option - direct and iterative solver options
(rheolef-7.2)
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.
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.
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).
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.
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.
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());
};
Pierre Saramito <Pierre.Saramito@imag.fr>
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.