
Control class for iterative solvers.
Used by iterative methods to determine whether the iteration should be continued. To this respect, the virtual function check() is called in each iteration with the current iteration step and the value indicating convergence (usually the residual).
After the iteration has terminated, the functions last_value and last_step can be used to obtain information about the final state of the iteration.
check() can be replaced in derived classes to allow for more sophisticated tests.
The return states of the check function are of type State, which is an enum local to this class. It indicates the state the solver is in.
The possible values of State are
iterate = 0: continue the iteration. success: the goal is reached, the iterative method can terminate successfully. failure: the iterative method should stop because convergence could not be achieved or at least was not achieved within the given maximal number of iterations. Definition at line 61 of file solver_control.h.
| enum SolverControl::State |
Enum denoting the different states a solver can be in. See the general documentation of this class for more information.
| iterate |
Continue iteration. |
| success |
Stop iteration, goal reached. |
| failure |
Stop iteration, goal not reached. |
Definition at line 72 of file solver_control.h.
| SolverControl::SolverControl | ( | const unsigned int | n = 100, |
| const double | tol = 1.e-10, |
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| const bool | log_history = false, |
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| const bool | log_result = true |
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| ) |
Constructor. The parameters n and tol are the maximum number of iteration steps before failure and the tolerance to determine success of the iteration.
log_history specifies whether the history (i.e. the value to be checked and the number of the iteration step) shall be printed to deallog stream. Default is: do not print. Similarly, log_result specifies the whether the final result is logged to deallog. Default is yes.
| virtual SolverControl::~SolverControl | ( | ) | [virtual] |
Virtual destructor is needed as there are virtual functions in this class.
| static void SolverControl::declare_parameters | ( | ParameterHandler & | param ) | [static] |
Interface to parameter file.
Reimplemented in ReductionControl.
| void SolverControl::parse_parameters | ( | ParameterHandler & | param ) |
Read parameters from file.
Reimplemented in ReductionControl.
Decide about success or failure of an iteration. This function gets the current iteration step to determine, whether the allowed number of steps has been exceeded and returns failure in this case. If check_value is below the prescribed tolerance, it returns success. In all other cases iterate is returned to suggest continuation of the iterative procedure.
The iteration is also aborted if the residual becomes a denormalized value (NaN). Note, however, that this check is only performed if the isnan function is provided by the operating system, which is not always true. The configure scripts checks for this and sets the flag HAVE_ISNAN in the file Make.global_options if this function was found.
check() additionally preserves step and check_value. These values are accessible by last_value() and last_step().
Derived classes may overload this function, e.g. to log the convergence indicators (check_value) or to do other computations.
Reimplemented in ReductionControl.
| State SolverControl::last_check | ( | ) | const |
Return the result of the last check operation.
| double SolverControl::initial_value | ( | ) | const |
Return the initial convergence criterion.
| double SolverControl::last_value | ( | ) | const |
Return the convergence value of last iteration step for which check was called by the solver.
| unsigned int SolverControl::last_step | ( | ) | const |
Number of last iteration step.
| unsigned int SolverControl::max_steps | ( | ) | const |
Maximum number of steps.
Referenced by ArpackSolver::solve().
| void SolverControl::set_failure_criterion | ( | const double | rel_failure_residual ) |
Enables the failure check. Solving is stopped with ReturnState failure if residual>failure_residual with failure_residual:=rel_failure_residual*first_residual.
| void SolverControl::clear_failure_criterion | ( | ) |
Disables failure check and resets relative_failure_residual and failure_residual to zero.
| double SolverControl::tolerance | ( | ) | const |
Tolerance.
Referenced by ArpackSolver::solve().
| double SolverControl::set_tolerance | ( | const | double ) |
Change tolerance.
| void SolverControl::enable_history_data | ( | ) |
Enables writing residuals of each step into a vector for later analysis.
| double SolverControl::average_reduction | ( | ) | const |
Average error reduction over all steps.
Requires enable_history_data()
| double SolverControl::final_reduction | ( | ) | const |
Error reduction of the last step; for stationary iterations, this approximates the norm of the iteration matrix.
Requires enable_history_data()
Error reduction of any iteration step.
Requires enable_history_data()
| void SolverControl::log_history | ( | const | bool ) |
Log each iteration step. Use log_frequency for skipping steps.
| bool SolverControl::log_history | ( | ) | const |
Returns the log_history flag.
| void SolverControl::log_result | ( | const | bool ) |
Log start and end step.
| bool SolverControl::log_result | ( | ) | const |
Returns the log_result flag.
| ::ExceptionBase& SolverControl::ExcHistoryDataRequired | ( | ) | [static] |
This exception is thrown if a function operating on the vector of history data of a SolverControl object id called, but storage of history data was not enabled by enable_history_data().
unsigned int SolverControl::maxsteps [protected] |
Maximum number of steps.
Definition at line 355 of file solver_control.h.
double SolverControl::tol [protected] |
Prescribed tolerance to be achieved.
Definition at line 360 of file solver_control.h.
State SolverControl::lcheck [protected] |
Result of last check operation.
Definition at line 365 of file solver_control.h.
double SolverControl::initial_val [protected] |
Initial value.
Definition at line 370 of file solver_control.h.
double SolverControl::lvalue [protected] |
Last value of the convergence criterion.
Definition at line 375 of file solver_control.h.
unsigned int SolverControl::lstep [protected] |
Last step.
Definition at line 380 of file solver_control.h.
bool SolverControl::check_failure [protected] |
Is set to true by set_failure_criterion and enables failure checking.
Definition at line 387 of file solver_control.h.
double SolverControl::relative_failure_residual [protected] |
Definition at line 394 of file solver_control.h.
double SolverControl::failure_residual [protected] |
failure_residual equals the first residual multiplied by relative_crit set by set_failure_criterion (see there).
Until the first residual is known it is 0.
Definition at line 405 of file solver_control.h.
bool SolverControl::m_log_history [protected] |
Log convergence history to deallog.
Definition at line 411 of file solver_control.h.
unsigned int SolverControl::m_log_frequency [protected] |
Log only every nth step.
Definition at line 415 of file solver_control.h.
bool SolverControl::m_log_result [protected] |
Log iteration result to deallog. If true, after finishing the iteration, a statement about failure or success together with lstep and lvalue are logged.
Definition at line 425 of file solver_control.h.
bool SolverControl::history_data_enabled [protected] |
Control over the storage of history data. Set by enable_history_data().
Definition at line 432 of file solver_control.h.
std::vector<double> SolverControl::history_data [protected] |
Vector storing the result after each iteration step for later statistical analysis.
Use of this vector is enabled by enable_history_data().
Definition at line 442 of file solver_control.h.
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