Line data    Source code

       1             : // The libMesh Finite Element Library.
       2             : // Copyright (C) 2002-2025 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
       3             : 
       4             : // This library is free software; you can redistribute it and/or
       5             : // modify it under the terms of the GNU Lesser General Public
       6             : // License as published by the Free Software Foundation; either
       7             : // version 2.1 of the License, or (at your option) any later version.
       8             : 
       9             : // This library is distributed in the hope that it will be useful,
      10             : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      11             : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12             : // Lesser General Public License for more details.
      13             : 
      14             : // You should have received a copy of the GNU Lesser General Public
      15             : // License along with this library; if not, write to the Free Software
      16             : // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
      17             : 
      18             : 
      19             : 
      20             : #ifndef LIBMESH_PRECONDITIONER_H
      21             : #define LIBMESH_PRECONDITIONER_H
      22             : 
      23             : 
      24             : // Local includes
      25             : #include "libmesh/libmesh_common.h"
      26             : #include "libmesh/reference_counted_object.h"
      27             : #include "libmesh/libmesh.h"
      28             : #include "libmesh/parallel_object.h"
      29             : 
      30             : // C++ includes
      31             : #include <cstddef>
      32             : 
      33             : namespace libMesh
      34             : {
      35             : 
      36             : // forward declarations
      37             : template <typename T> class SparseMatrix;
      38             : template <typename T> class NumericVector;
      39             : template <typename T> class ShellMatrix;
      40             : enum SolverPackage : int;
      41             : enum PreconditionerType : int;
      42             : 
      43             : /**
      44             :  * This class provides a uniform interface for preconditioners.  This base
      45             :  * class can be inherited from to wrap preconditioners from different packages
      46             :  * like PETSc or Trilinos.
      47             :  *
      48             :  * In the below comments P is the matrix to be preconditioned with Apply()
      49             :  * performing the equivalent of the matrix vector product P^-1 x.  This
      50             :  * can also be thought of as (usually approximately) solving for Py=x.
      51             :  *
      52             :  * \author Derek Gaston
      53             :  * \date 2009
      54             :  */
      55             : template <typename T>
      56             : class Preconditioner : public ReferenceCountedObject<Preconditioner<T>>,
      57             :                        public ParallelObject
      58             : {
      59             : public:
      60             : 
      61             :   /**
      62             :    * Constructor. Initializes Preconditioner data structures.
      63             :    */
      64             :   Preconditioner (const libMesh::Parallel::Communicator & comm);
      65             : 
      66             :   /**
      67             :    * Destructor.
      68             :    */
      69             :   virtual ~Preconditioner ();
      70             : 
      71             :   /**
      72             :    * Builds a \p Preconditioner using the linear solver package
      73             :    * specified by \p solver_package, returning the result wrapped in a
      74             :    * std::unique_ptr for safety.
      75             :    */
      76             :   static std::unique_ptr<Preconditioner<T>>
      77             :   build_preconditioner(const libMesh::Parallel::Communicator & comm,
      78             :                        const SolverPackage solver_package = libMesh::default_solver_package());
      79             : 
      80             :   /**
      81             :    * \returns \p true if the data structures are initialized, \p false
      82             :    * otherwise.
      83             :    */
      84           0 :   virtual bool initialized () const { return _is_initialized; }
      85             : 
      86             :   /**
      87             :    * Computes the preconditioned vector \p y based on input vector \p
      88             :    * x. This is usually done by solving \f$ Py=x \f$ to get the
      89             :    * action of \f$ P^-1 x \f$.
      90             :    */
      91             :   virtual void apply(const NumericVector<T> & x, NumericVector<T> & y) = 0;
      92             : 
      93             :   /**
      94             :    * Release all memory and clear data structures.
      95             :    */
      96          10 :   virtual void clear () {}
      97             : 
      98             :   /**
      99             :    * Initialize data structures if not done so already.
     100             :    *
     101             :    * \note This MUST be called before the preconditioning object is used.
     102             :    */
     103           0 :   virtual void init () {}
     104             : 
     105             :   /**
     106             :    * This is called every time the "operator might have changed".
     107             :    *
     108             :    * This is where you need to fill in your preconditioning matrix.
     109             :    */
     110           0 :   virtual void setup () {}
     111             : 
     112             :   /**
     113             :    * Can be used to zero items relevant to the preconditioner
     114             :    */
     115           0 :   virtual void zero() {}
     116             : 
     117             :   /**
     118             :    * Sets the matrix to be preconditioned.
     119             :    */
     120             :   void set_matrix(SparseMatrix<Number> & mat);
     121             : 
     122             :   /**
     123             :    * \returns The type of preconditioner to use.
     124             :    */
     125           0 :   PreconditionerType type () const { return _preconditioner_type; }
     126             : 
     127             :   /**
     128             :    * Sets the type of preconditioner to use.
     129             :    */
     130             :   void set_type (const PreconditionerType pct);
     131             : 
     132             : protected:
     133             : 
     134             :   /**
     135             :    * The matrix P... ie the matrix to be preconditioned.
     136             :    * This is often the actual system matrix of a linear system.
     137             :    */
     138             :   SparseMatrix<T> * _matrix;
     139             : 
     140             :   /**
     141             :    * Enum stating with type of preconditioner to use.
     142             :    */
     143             :   PreconditionerType _preconditioner_type;
     144             : 
     145             :   /**
     146             :    * Flag indicating if the data structures have been initialized.
     147             :    */
     148             :   bool _is_initialized;
     149             : };
     150             : 
     151             : 
     152             : 
     153             : 
     154             : /*----------------------- inline functions ----------------------------------*/
     155             : template <typename T>
     156             : inline
     157          10 : Preconditioner<T>::~Preconditioner ()
     158             : {
     159          10 :   this->clear ();
     160          10 : }
     161             : 
     162             : template <typename T>
     163             : void
     164          14 : Preconditioner<T>::set_matrix(SparseMatrix<Number> & mat)
     165             : {
     166             :   //If the matrix is changing then we (probably) need to reinitialize.
     167         490 :   _is_initialized = false;
     168         292 :   _matrix = &mat;
     169         212 : }
     170             : 
     171             : template <typename T>
     172             : void
     173           0 : Preconditioner<T>::set_type (const PreconditionerType pct)
     174             : {
     175             :   //If the preconditioner type changes we (probably) need to reinitialize.
     176           0 :   _is_initialized = false;
     177           0 :   _preconditioner_type = pct;
     178           0 : }
     179             : 
     180             : } // namespace libMesh
     181             : 
     182             : 
     183             : #endif // LIBMESH_PRECONDITIONER_H