FixedSubcyclingTimeSteppingCodeSnippets.py

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# This file is part of the ExaHyPE2 project. For conditions of distribution and 
# use, please see the copyright notice at www.peano-framework.org
from .SolverCodeSnippets import SolverCodeSnippets
 
 
class FixedSubcyclingTimeSteppingCodeSnippets( SolverCodeSnippets ):
  """
  
  Code snippet generator for all subcycling solvers
  
  """
  
  def __init__(self, remove_accumulation_errors):
    self._remove_accumulation_errors = remove_accumulation_errors
 
 
  def create_abstract_solver_user_declarations(self):
    return """
private:
  double _finestMeshTimeStepSize;
public:
  double getTimeStepSize() const;  
    """  
 
 
  def create_abstract_solver_user_definitions(self):
    return """
void {{FULL_QUALIFIED_NAMESPACE}}::{{CLASSNAME}}::setMaxEigenvalue( double eigenvalue ) {
  if ( tarch::la::greater( eigenvalue, 0.0 ) ) {
    tarch::multicore::Lock lock(_semaphore);
    _maxEigenvalue = std::max(_maxEigenvalue,eigenvalue);
  }
}    
 
 
double {{FULL_QUALIFIED_NAMESPACE}}::{{CLASSNAME}}::getAdmissibleTimeStepSize() const {
  return _admissibleTimeStepSize;
}
    """  
 
 
  def create_abstract_solver_constructor_statements(self):
    return "_admissibleTimeStepSize = 0.0;"
  
  
  def create_compute_time_step_size(self):
    if self._remove_accumulation_errors:
      return """
  // The fixed solver's _timeStepSize scales with min volume h, i.e. it is 
  // always chosen such that the finest grid does something meaningful.
  const double originalStepSize = repositories::{{SOLVER_INSTANCE}}.getMinPatchSize()>0.0 ?
    repositories::{{SOLVER_INSTANCE}}.getTimeStepSize() * marker.h()(0) / repositories::{{SOLVER_INSTANCE}}.getMinPatchSize(false) :
    0.0;
  double timeStepSize = ::exahype2::removeTimeStepAccumulationErrorsFromCell( fineGridCell{{SOLVER_NAME}}CellLabel, fineGridFaces{{SOLVER_NAME}}FaceLabel, originalStepSize);
"""  
    else:
      return """
  // The fixed solver's _timeStepSize scales with min volume h, i.e. it is 
  // always chosen such that the finest grid does something meaningful.
  double timeStepSize = repositories::{{SOLVER_INSTANCE}}.getMinPatchSize()>0.0 ?
    repositories::{{SOLVER_INSTANCE}}.getTimeStepSize() * marker.h()(0) / repositories::{{SOLVER_INSTANCE}}.getMinPatchSize(false) :
    0.0;
"""  
 
  
  def create_compute_new_time_step_size(self):
    """
    
    This is global, fixed time stepping, i.e. the new time step size will likely
    be the same as the previous one, unless the mesh changes, as we work with 
    normalised time step sizes, i.e. in this case the time step size might change.
    Anyway, the new time step size is only for stats anyway, as we'll pick a 
    global one when we determine timeStepSize the next time step.
    
    """
    return """
    repositories::{{SOLVER_INSTANCE}}.setMaxEigenvalue( maxEigenvalue );  
    
    // This is a value set for stats reasons. We'll ignore it later as we 
    // ask for a new valid time step size from getAdmissibleTimeStepSize().
    const double newTimeStepSize = repositories::{{SOLVER_INSTANCE}}.getAdmissibleTimeStepSize();
"""
 
 
  def create_finish_time_step_implementation(self):
    """
  
    This routine is inserted after we have reduced all global quantities. These
    are the quantities with the postfix ThisTimeStep.
  
    """ 
    return """
  if (isLastGridSweepOfTimeStep()) {
    #ifdef Parallel
    double newMaxEigenvalue = _maxEigenvalue;
    tarch::mpi::Rank::getInstance().allReduce(
        &newMaxEigenvalue,
        &_maxEigenvalue,
        1,
        MPI_DOUBLE,
        MPI_MAX, 
        [&]() -> void { tarch::services::ServiceRepository::getInstance().receiveDanglingMessages(); }
        );
    #endif
 
    if ( tarch::la::smaller(_maxEigenvalue, 0.0 ) ) {
      ::tarch::triggerNonCriticalAssertion( __FILE__, __LINE__, "_maxEigenvalue>=0", "invalid max eigenvalue: " + std::to_string(_maxEigenvalue) );
      // keep time step size invariant
      // _admissibleTimeStepSize = _admissibleTimeStepSize;
    }
    else if ( tarch::la::equals(_maxEigenvalue, 0.0 ) ) {
      logWarning( "finishTimeStep(...)", "maximum eigenvalue approaches 0.0. For nonlinear PDEs, this often means the PDE becomes stationary. It could also be a bug however" ); 
      _admissibleTimeStepSize = 0.0;
    }
  }
"""