Reference documentation for deal.II version GIT 9c182271f7 20230328 14:30:01+00:00

#include <deal.II/lac/solver_cg.h>
Classes  
struct  AdditionalData 
Public Types  
using  size_type = types::global_dof_index 
using  vector_type = Vector< double > 
Public Member Functions  
SolverFlexibleCG (SolverControl &cn, VectorMemory< VectorType > &mem, const AdditionalData &data=AdditionalData())  
SolverFlexibleCG (SolverControl &cn, const AdditionalData &data=AdditionalData())  
void  solve (const MatrixType &A, Vector< double > &x, const Vector< double > &b, const PreconditionerType &preconditioner) 
boost::signals2::connection  connect_coefficients_slot (const std::function< void(typename VectorType::value_type, typename VectorType::value_type)> &slot) 
boost::signals2::connection  connect_condition_number_slot (const std::function< void(double)> &slot, const bool every_iteration=false) 
boost::signals2::connection  connect_eigenvalues_slot (const std::function< void(const std::vector< double > &)> &slot, const bool every_iteration=false) 
boost::signals2::connection  connect (const std::function< SolverControl::State(const unsigned int iteration, const double check_value, const Vector< double > ¤t_iterate)> &slot) 
template<class Archive >  
void  serialize (Archive &ar, const unsigned int version) 
Subscriptor functionality  
Classes derived from Subscriptor provide a facility to subscribe to this object. This is mostly used by the SmartPointer class.  
void  subscribe (std::atomic< bool > *const validity, const std::string &identifier="") const 
void  unsubscribe (std::atomic< bool > *const validity, const std::string &identifier="") const 
unsigned int  n_subscriptions () const 
template<typename StreamType >  
void  list_subscribers (StreamType &stream) const 
void  list_subscribers () const 
Static Public Member Functions  
static ::ExceptionBase &  ExcInUse (int arg1, std::string arg2, std::string arg3) 
static ::ExceptionBase &  ExcNoSubscriber (std::string arg1, std::string arg2) 
Protected Member Functions  
virtual void  print_vectors (const unsigned int step, const Vector< double > &x, const Vector< double > &r, const Vector< double > &d) const 
Static Protected Member Functions  
static void  compute_eigs_and_cond (const std::vector< typename VectorType::value_type > &diagonal, const std::vector< typename VectorType::value_type > &offdiagonal, const boost::signals2::signal< void(const std::vector< double > &)> &eigenvalues_signal, const boost::signals2::signal< void(double)> &cond_signal) 
Protected Attributes  
AdditionalData  additional_data 
boost::signals2::signal< void(typename VectorType::value_type, typename VectorType::value_type)>  coefficients_signal 
boost::signals2::signal< void(double)>  condition_number_signal 
boost::signals2::signal< void(double)>  all_condition_numbers_signal 
boost::signals2::signal< void(const std::vector< double > &)>  eigenvalues_signal 
boost::signals2::signal< void(const std::vector< double > &)>  all_eigenvalues_signal 
bool  determine_beta_by_flexible_formula 
GrowingVectorMemory< Vector< double > >  static_vector_memory 
VectorMemory< Vector< double > > &  memory 
boost::signals2::signal< SolverControl::State(const unsigned int iteration, const double check_value, const Vector< double > ¤t_iterate), StateCombiner >  iteration_status 
Private Types  
using  map_value_type = decltype(counter_map)::value_type 
using  map_iterator = decltype(counter_map)::iterator 
Private Member Functions  
void  check_no_subscribers () const noexcept 
Private Attributes  
std::atomic< unsigned int >  counter 
std::map< std::string, unsigned int >  counter_map 
std::vector< std::atomic< bool > * >  validity_pointers 
const std::type_info *  object_info 
Static Private Attributes  
static std::mutex  mutex 
This class implements a flexible variant of the conjugate gradient method, which is based on a different formula to compute \(\beta_k\) in the process of constructing a new search direction that is Aorthogonal against the previous one. Rather than using the Fletcher–Reeves update formula with \(\beta_k = \frac{\mathbf{r}^T_{k+1} \mathbf{z}_{k+1}}{\mathbf{r}^T_{k} \mathbf{z}_{k}}\) for computing the new search direction (here \(\mathbf{r}_{k+1}\) is the residual in step \(k+1\) and \(\mathbf{z}_{k+1} = P^{1} \mathbf{r}_{k+1}\)) as in the classical conjugate gradient algorithm, this class selects the PolakRibiere formula \(\beta_k = \frac{\mathbf{r}^T_{k+1} \left(\mathbf{z}_{k+1}  \mathbf{z}_{k}\right)}{\mathbf{r}^T_{k} \mathbf{z}_{k}}\). The additional term \(\mathbf{r}^T_{k+1} \mathbf{z}_{k}\) is zero for linear symmetricpositive definite preconditioners due to the construction of the search directions, so the behavior of SolverFlexibleCG is equivalent for those kinds of situations and merely increases costs by requiring an additional stored vector and associated vector operations. While there are no theoretical guarantees for convergence as in the classical CG algorithm, the current class has been documented to be much more robust for variable preconditioners (e.g., involving some iterative inverse that is not fully converged) or a preconditioner with some slight nonsymmetry (like weighted Schwarz methods), which results from the local optimality of the search direction with at least as good progress as the locally optimal steepest descent method.
Definition at line 354 of file solver_cg.h.
using SolverFlexibleCG< VectorType >::size_type = types::global_dof_index 
Declare type for container size.
Definition at line 360 of file solver_cg.h.

inherited 

privateinherited 
The data type used in counter_map.
Definition at line 230 of file subscriptor.h.

privateinherited 
The iterator type used in counter_map.
Definition at line 235 of file subscriptor.h.
SolverFlexibleCG< VectorType >::SolverFlexibleCG  (  SolverControl &  cn, 
VectorMemory< VectorType > &  mem,  
const AdditionalData &  data = AdditionalData() 

) 
Constructor.
SolverFlexibleCG< VectorType >::SolverFlexibleCG  (  SolverControl &  cn, 
const AdditionalData &  data = AdditionalData() 

) 
Constructor. Use an object of type GrowingVectorMemory as a default to allocate memory.

inherited 
Solve the linear system \(Ax=b\) for x.

inherited 
Connect a slot to retrieve the CG coefficients. The slot will be called with alpha as the first argument and with beta as the second argument, where alpha and beta follow the notation in Y. Saad: "Iterative methods for Sparse Linear Systems", section 6.7. Called once per iteration

inherited 
Connect a slot to retrieve the estimated condition number. Called on each iteration if every_iteration=true, otherwise called once when iterations are ended (i.e., either because convergence has been achieved, or because divergence has been detected).

inherited 
Connect a slot to retrieve the estimated eigenvalues. Called on each iteration if every_iteration=true, otherwise called once when iterations are ended (i.e., either because convergence has been achieved, or because divergence has been detected).

protectedvirtualinherited 
Interface for derived class. This function gets the current iteration vector, the residual and the update vector in each step. It can be used for graphical output of the convergence history.

staticprotectedinherited 
Estimates the eigenvalues from diagonal and offdiagonal. Uses these estimate to compute the condition number. Calls the signals eigenvalues_signal and cond_signal with these estimates as arguments.

inherited 
Connect a function object that will be called periodically within iterative solvers. This function is used to attach monitors to iterative solvers, either to determine when convergence has happened, or simply to observe the progress of an iteration. See the documentation of this class for more information.
slot  A function object specified here will, with each call, receive the number of the current iteration, the value that is used to check for convergence (typically the residual of the current iterate with respect to the linear system to be solved) and the currently best available guess for the current iterate. Note that some solvers do not update the approximate solution in every iteration but only after convergence or failure has been determined (GMRES is an example); in such cases, the vector passed as the last argument to the signal is simply the best approximate at the time the signal is called, but not the vector that will be returned if the signal's return value indicates that the iteration should be terminated. The function object must return a SolverControl::State value that indicates whether the iteration should continue, has failed, or has succeeded. The results of all connected functions will then be combined to determine what should happen with the iteration. 

inherited 
Subscribes a user of the object by storing the pointer validity
. The subscriber may be identified by text supplied as identifier
.
Definition at line 136 of file subscriptor.cc.

inherited 
Unsubscribes a user from the object.
identifier
and the validity
pointer must be the same as the one supplied to subscribe(). Definition at line 156 of file subscriptor.cc.

inlineinherited 
Return the present number of subscriptions to this object. This allows to use this class for reference counted lifetime determination where the last one to unsubscribe also deletes the object.
Definition at line 300 of file subscriptor.h.

inlineinherited 
List the subscribers to the input stream
.
Definition at line 317 of file subscriptor.h.

inherited 
List the subscribers to deallog
.
Definition at line 204 of file subscriptor.cc.

inlineinherited 
Read or write the data of this object to or from a stream for the purpose of serialization using the BOOST serialization library.
This function does not actually serialize any of the member variables of this class. The reason is that what this class stores is only who subscribes to this object, but who does so at the time of storing the contents of this object does not necessarily have anything to do with who subscribes to the object when it is restored. Consequently, we do not want to overwrite the subscribers at the time of restoring, and then there is no reason to write the subscribers out in the first place.
Definition at line 309 of file subscriptor.h.

privatenoexceptinherited 
Check that there are no objects subscribing to this object. If this check passes then it is safe to destroy the current object. It this check fails then this function will either abort or print an error message to deallog (by using the AssertNothrow mechanism), but will not throw an exception.
Definition at line 53 of file subscriptor.cc.

protectedinherited 
Additional parameters.
Definition at line 281 of file solver_cg.h.

protectedinherited 
Signal used to retrieve the CG coefficients. Called on each iteration.
Definition at line 288 of file solver_cg.h.

protectedinherited 
Signal used to retrieve the estimated condition number. Called once when all iterations are ended.
Definition at line 294 of file solver_cg.h.

protectedinherited 
Signal used to retrieve the estimated condition numbers. Called on each iteration.
Definition at line 300 of file solver_cg.h.

protectedinherited 
Signal used to retrieve the estimated eigenvalues. Called once when all iterations are ended.
Definition at line 306 of file solver_cg.h.

protectedinherited 
Signal used to retrieve the estimated eigenvalues. Called on each iteration.
Definition at line 313 of file solver_cg.h.
Flag to indicate whether the classical Fletcher–Reeves update formula for the parameter \(\beta_k\) (standard CG algorithm, minimal storage needs) or the flexible conjugate gradient method with PolakRibiere formula for \(\beta_k\) should be used. This base class implementation of SolverCG will always use the former method, whereas the derived class SolverFlexibleCG will use the latter.
Definition at line 323 of file solver_cg.h.

mutableprotectedinherited 

protectedinherited 

protectedinherited 
A signal that iterative solvers can execute at the end of every iteration (or in an otherwise periodic fashion) to find out whether we should continue iterating or not. The signal may call one or more slots that each will make this determination by themselves, and the result over all slots (function calls) will be determined by the StateCombiner object.
The arguments passed to the signal are (i) the number of the current iteration; (ii) the value that is used to determine convergence (oftentimes the residual, but in other cases other quantities may be used as long as they converge to zero as the iterate approaches the solution of the linear system); and (iii) a vector that corresponds to the current best guess for the solution at the point where the signal is called. Note that some solvers do not update the approximate solution in every iteration but only after convergence or failure has been determined (GMRES is an example); in such cases, the vector passed as the last argument to the signal is simply the best approximate at the time the signal is called, but not the vector that will be returned if the signal's return value indicates that the iteration should be terminated.

mutableprivateinherited 
Store the number of objects which subscribed to this object. Initially, this number is zero, and upon destruction it shall be zero again (i.e. all objects which subscribed should have unsubscribed again).
The creator (and owner) of an object is counted in the map below if HE manages to supply identification.
We use the mutable
keyword in order to allow subscription to constant objects also.
This counter may be read from and written to concurrently in multithreaded code: hence we use the std::atomic
class template.
Definition at line 219 of file subscriptor.h.

mutableprivateinherited 
In this map, we count subscriptions for each different identification string supplied to subscribe().
Definition at line 225 of file subscriptor.h.

mutableprivateinherited 
In this vector, we store pointers to the validity bool in the SmartPointer objects that subscribe to this class.
Definition at line 241 of file subscriptor.h.

mutableprivateinherited 
Pointer to the typeinfo object of this object, from which we can later deduce the class name. Since this information on the derived class is neither available in the destructor, nor in the constructor, we obtain it in between and store it here.
Definition at line 249 of file subscriptor.h.

staticprivateinherited 
A mutex used to ensure data consistency when printing out the list of subscribers.
Definition at line 271 of file subscriptor.h.