void MeshRefinement::flag_elements_by_error_tolerance (const ErrorVector & error_per_cell_in)
{
parallel_object_only();
libmesh_assert_greater (_coarsen_threshold, 0);
// Check for valid fractions..
// The fraction values must be in [0,1]
libmesh_assert_greater_equal (_refine_fraction, 0);
libmesh_assert_less_equal (_refine_fraction, 1);
libmesh_assert_greater_equal (_coarsen_fraction, 0);
libmesh_assert_less_equal (_coarsen_fraction, 1);
// How much error per cell will we tolerate?
const Real local_refinement_tolerance =
_absolute_global_tolerance / std::sqrt(static_cast<Real>(_mesh.n_active_elem()));
const Real local_coarsening_tolerance =
local_refinement_tolerance * _coarsen_threshold;
// Prepare another error vector if we need to sum parent errors
ErrorVector error_per_parent;
if (_coarsen_by_parents)
{
Real parent_error_min, parent_error_max;
create_parent_error_vector(error_per_cell_in,
error_per_parent,
parent_error_min,
parent_error_max);
}
for (auto & elem : _mesh.active_element_ptr_range())
{
Elem * parent = elem->parent();
const dof_id_type elem_number = elem->id();
const ErrorVectorReal elem_error = error_per_cell_in[elem_number];
if (elem_error > local_refinement_tolerance &&
elem->level() < _max_h_level)
elem->set_refinement_flag(Elem::REFINE);
if (!_coarsen_by_parents && elem_error <
local_coarsening_tolerance)
elem->set_refinement_flag(Elem::COARSEN);
if (_coarsen_by_parents && parent)
{
ErrorVectorReal parent_error = error_per_parent[parent->id()];
if (parent_error >= 0.)
{
const Real parent_coarsening_tolerance =
std::sqrt(parent->n_children() *
local_coarsening_tolerance *
local_coarsening_tolerance);
if (parent_error < parent_coarsening_tolerance)
elem->set_refinement_flag(Elem::COARSEN);
}
}
}
}
void MeshRefinement::flag_elements_by_elem_fraction (const ErrorVector& error_per_cell,
const Real refine_frac,
const Real coarsen_frac,
const unsigned int max_l)
{
parallel_only();
// The function arguments are currently just there for
// backwards_compatibility
if (!_use_member_parameters)
{
// If the user used non-default parameters, lets warn
// that they're deprecated
if (refine_frac != 0.3 ||
coarsen_frac != 0.0 ||
max_l != libMesh::invalid_uint)
libmesh_deprecated();
_refine_fraction = refine_frac;
_coarsen_fraction = coarsen_frac;
_max_h_level = max_l;
}
// Check for valid fractions..
// The fraction values must be in [0,1]
libmesh_assert_greater_equal (_refine_fraction, 0);
libmesh_assert_less_equal (_refine_fraction, 1);
libmesh_assert_greater_equal (_coarsen_fraction, 0);
libmesh_assert_less_equal (_coarsen_fraction, 1);
// The number of active elements in the mesh
const unsigned int n_active_elem = _mesh.n_elem();
// The number of elements to flag for coarsening
const unsigned int n_elem_coarsen =
static_cast<unsigned int>(_coarsen_fraction * n_active_elem);
// The number of elements to flag for refinement
const unsigned int n_elem_refine =
static_cast<unsigned int>(_refine_fraction * n_active_elem);
// Clean up the refinement flags. These could be left
// over from previous refinement steps.
this->clean_refinement_flags();
// This vector stores the error and element number for all the
// active elements. It will be sorted and the top & bottom
// elements will then be flagged for coarsening & refinement
std::vector<float> sorted_error;
sorted_error.reserve (n_active_elem);
// Loop over the active elements and create the entry
// in the sorted_error vector
MeshBase::element_iterator elem_it = _mesh.active_local_elements_begin();
const MeshBase::element_iterator elem_end = _mesh.active_local_elements_end();
for (; elem_it != elem_end; ++elem_it)
sorted_error.push_back (error_per_cell[(*elem_it)->id()]);
CommWorld.allgather(sorted_error);
// Now sort the sorted_error vector
std::sort (sorted_error.begin(), sorted_error.end());
// If we're coarsening by parents:
// Create a sorted error vector with coarsenable parent elements
// only, sorted by lowest errors first
ErrorVector error_per_parent, sorted_parent_error;
if (_coarsen_by_parents)
{
Real parent_error_min, parent_error_max;
create_parent_error_vector(error_per_cell,
error_per_parent,
parent_error_min,
parent_error_max);
sorted_parent_error = error_per_parent;
std::sort (sorted_parent_error.begin(), sorted_parent_error.end());
// All the other error values will be 0., so get rid of them.
sorted_parent_error.erase (std::remove(sorted_parent_error.begin(),
sorted_parent_error.end(), 0.),
sorted_parent_error.end());
}
float top_error= 0., bottom_error = 0.;
// Get the maximum error value corresponding to the
// bottom n_elem_coarsen elements
if (_coarsen_by_parents && n_elem_coarsen)
{
const unsigned int dim = _mesh.mesh_dimension();
unsigned int twotodim = 1;
for (unsigned int i=0; i!=dim; ++i)
twotodim *= 2;
unsigned int n_parent_coarsen = n_elem_coarsen / (twotodim - 1);
if (n_parent_coarsen)
bottom_error = sorted_parent_error[n_parent_coarsen - 1];
}
else if (n_elem_coarsen)
{
bottom_error = sorted_error[n_elem_coarsen - 1];
}
if (n_elem_refine)
top_error = sorted_error[sorted_error.size() - n_elem_refine];
// Finally, let's do the element flagging
elem_it = _mesh.active_elements_begin();
for (; elem_it != elem_end; ++elem_it)
{
Elem* elem = *elem_it;
Elem* parent = elem->parent();
if (_coarsen_by_parents && parent && n_elem_coarsen &&
error_per_parent[parent->id()] <= bottom_error)
elem->set_refinement_flag(Elem::COARSEN);
if (!_coarsen_by_parents && n_elem_coarsen &&
error_per_cell[elem->id()] <= bottom_error)
elem->set_refinement_flag(Elem::COARSEN);
if (n_elem_refine &&
elem->level() < _max_h_level &&
error_per_cell[elem->id()] >= top_error)
elem->set_refinement_flag(Elem::REFINE);
}
}
//-----------------------------------------------------------------
// Mesh refinement methods
void MeshRefinement::flag_elements_by_error_fraction (const ErrorVector& error_per_cell,
const Real refine_frac,
const Real coarsen_frac,
const unsigned int max_l)
{
parallel_only();
// The function arguments are currently just there for
// backwards_compatibility
if (!_use_member_parameters)
{
// If the user used non-default parameters, lets warn
// that they're deprecated
if (refine_frac != 0.3 ||
coarsen_frac != 0.0 ||
max_l != libMesh::invalid_uint)
libmesh_deprecated();
_refine_fraction = refine_frac;
_coarsen_fraction = coarsen_frac;
_max_h_level = max_l;
}
// Check for valid fractions..
// The fraction values must be in [0,1]
libmesh_assert_greater_equal (_refine_fraction, 0);
libmesh_assert_less_equal (_refine_fraction, 1);
libmesh_assert_greater_equal (_coarsen_fraction, 0);
libmesh_assert_less_equal (_coarsen_fraction, 1);
// Clean up the refinement flags. These could be left
// over from previous refinement steps.
this->clean_refinement_flags();
// We're getting the minimum and maximum error values
// for the ACTIVE elements
Real error_min = 1.e30;
Real error_max = 0.;
// And, if necessary, for their parents
Real parent_error_min = 1.e30;
Real parent_error_max = 0.;
// Prepare another error vector if we need to sum parent errors
ErrorVector error_per_parent;
if (_coarsen_by_parents)
{
create_parent_error_vector(error_per_cell,
error_per_parent,
parent_error_min,
parent_error_max);
}
// We need to loop over all active elements to find the minimum
MeshBase::element_iterator el_it =
_mesh.active_local_elements_begin();
const MeshBase::element_iterator el_end =
_mesh.active_local_elements_end();
for (; el_it != el_end; ++el_it)
{
const unsigned int id = (*el_it)->id();
libmesh_assert_less (id, error_per_cell.size());
error_max = std::max (error_max, error_per_cell[id]);
error_min = std::min (error_min, error_per_cell[id]);
}
CommWorld.max(error_max);
CommWorld.min(error_min);
// Compute the cutoff values for coarsening and refinement
const Real error_delta = (error_max - error_min);
const Real parent_error_delta = parent_error_max - parent_error_min;
const Real refine_cutoff = (1.- _refine_fraction)*error_max;
const Real coarsen_cutoff = _coarsen_fraction*error_delta + error_min;
const Real parent_cutoff = _coarsen_fraction*parent_error_delta + error_min;
// // Print information about the error
// libMesh::out << " Error Information:" << std::endl
// << " ------------------" << std::endl
// << " min: " << error_min << std::endl
// << " max: " << error_max << std::endl
// << " delta: " << error_delta << std::endl
// << " refine_cutoff: " << refine_cutoff << std::endl
// << " coarsen_cutoff: " << coarsen_cutoff << std::endl;
// Loop over the elements and flag them for coarsening or
// refinement based on the element error
MeshBase::element_iterator e_it =
_mesh.active_elements_begin();
const MeshBase::element_iterator e_end =
_mesh.active_elements_end();
for (; e_it != e_end; ++e_it)
{
Elem* elem = *e_it;
const unsigned int id = elem->id();
libmesh_assert_less (id, error_per_cell.size());
const float elem_error = error_per_cell[id];
if (_coarsen_by_parents)
{
Elem* parent = elem->parent();
if (parent)
{
const unsigned int parentid = parent->id();
if (error_per_parent[parentid] >= 0. &&
error_per_parent[parentid] <= parent_cutoff)
elem->set_refinement_flag(Elem::COARSEN);
}
}
// Flag the element for coarsening if its error
// is <= coarsen_fraction*delta + error_min
else if (elem_error <= coarsen_cutoff)
{
elem->set_refinement_flag(Elem::COARSEN);
}
// Flag the element for refinement if its error
// is >= refinement_cutoff.
if (elem_error >= refine_cutoff)
if (elem->level() < _max_h_level)
elem->set_refinement_flag(Elem::REFINE);
}
}
bool MeshRefinement::flag_elements_by_nelem_target (const ErrorVector& error_per_cell)
{
parallel_only();
// Check for valid fractions..
// The fraction values must be in [0,1]
libmesh_assert_greater_equal (_refine_fraction, 0);
libmesh_assert_less_equal (_refine_fraction, 1);
libmesh_assert_greater_equal (_coarsen_fraction, 0);
libmesh_assert_less_equal (_coarsen_fraction, 1);
// This function is currently only coded to work when coarsening by
// parents - it's too hard to guess how many coarsenings will be
// performed otherwise.
libmesh_assert (_coarsen_by_parents);
// The number of active elements in the mesh - hopefully less than
// 2 billion on 32 bit machines
const unsigned int n_active_elem = _mesh.n_active_elem();
// The maximum number of active elements to flag for coarsening
const unsigned int max_elem_coarsen =
static_cast<unsigned int>(_coarsen_fraction * n_active_elem) + 1;
// The maximum number of elements to flag for refinement
const unsigned int max_elem_refine =
static_cast<unsigned int>(_refine_fraction * n_active_elem) + 1;
// Clean up the refinement flags. These could be left
// over from previous refinement steps.
this->clean_refinement_flags();
// The target number of elements to add or remove
const int n_elem_new = _nelem_target - n_active_elem;
// Create an vector with active element errors and ids,
// sorted by highest errors first
const unsigned int max_elem_id = _mesh.max_elem_id();
std::vector<std::pair<float, unsigned int> > sorted_error;
sorted_error.reserve (n_active_elem);
// On a ParallelMesh, we need to communicate to know which remote ids
// correspond to active elements.
{
std::vector<bool> is_active(max_elem_id, false);
MeshBase::element_iterator elem_it = _mesh.active_local_elements_begin();
const MeshBase::element_iterator elem_end = _mesh.active_local_elements_end();
for (; elem_it != elem_end; ++elem_it)
{
const unsigned int eid = (*elem_it)->id();
is_active[eid] = true;
libmesh_assert_less (eid, error_per_cell.size());
sorted_error.push_back
(std::make_pair(error_per_cell[eid], eid));
}
CommWorld.max(is_active);
CommWorld.allgather(sorted_error);
}
// Default sort works since pairs are sorted lexicographically
std::sort (sorted_error.begin(), sorted_error.end());
std::reverse (sorted_error.begin(), sorted_error.end());
// Create a sorted error vector with coarsenable parent elements
// only, sorted by lowest errors first
ErrorVector error_per_parent;
std::vector<std::pair<float, unsigned int> > sorted_parent_error;
Real parent_error_min, parent_error_max;
create_parent_error_vector(error_per_cell,
error_per_parent,
parent_error_min,
parent_error_max);
// create_parent_error_vector sets values for non-parents and
// non-coarsenable parents to -1. Get rid of them.
for (unsigned int i=0; i != error_per_parent.size(); ++i)
if (error_per_parent[i] != -1)
sorted_parent_error.push_back(std::make_pair(error_per_parent[i], i));
std::sort (sorted_parent_error.begin(), sorted_parent_error.end());
// Keep track of how many elements we plan to coarsen & refine
unsigned int coarsen_count = 0;
unsigned int refine_count = 0;
const unsigned int dim = _mesh.mesh_dimension();
unsigned int twotodim = 1;
for (unsigned int i=0; i!=dim; ++i)
twotodim *= 2;
// First, let's try to get our element count to target_nelem
if (n_elem_new >= 0)
{
// Every element refinement creates at least
// 2^dim-1 new elements
refine_count =
std::min(static_cast<unsigned int>(n_elem_new / (twotodim-1)),
max_elem_refine);
}
else
{
// Every successful element coarsening is likely to destroy
// 2^dim-1 net elements.
coarsen_count =
std::min(static_cast<unsigned int>(-n_elem_new / (twotodim-1)),
max_elem_coarsen);
}
// Next, let's see if we can trade any refinement for coarsening
while (coarsen_count < max_elem_coarsen &&
refine_count < max_elem_refine &&
coarsen_count < sorted_parent_error.size() &&
refine_count < sorted_error.size() &&
sorted_error[refine_count].first >
sorted_parent_error[coarsen_count].first * _coarsen_threshold)
{
coarsen_count++;
refine_count++;
}
// On a ParallelMesh, we need to communicate to know which remote ids
// correspond to refinable elements
unsigned int successful_refine_count = 0;
{
std::vector<bool> is_refinable(max_elem_id, false);
for (unsigned int i=0; i != sorted_error.size(); ++i)
{
unsigned int eid = sorted_error[i].second;
Elem *elem = _mesh.query_elem(eid);
if (elem && elem->level() < _max_h_level)
is_refinable[eid] = true;
}
CommWorld.max(is_refinable);
if (refine_count > max_elem_refine)
refine_count = max_elem_refine;
for (unsigned int i=0; i != sorted_error.size(); ++i)
{
if (successful_refine_count >= refine_count)
break;
unsigned int eid = sorted_error[i].second;
Elem *elem = _mesh.query_elem(eid);
if (is_refinable[eid])
{
if (elem)
elem->set_refinement_flag(Elem::REFINE);
successful_refine_count++;
}
}
}
// If we couldn't refine enough elements, don't coarsen too many
// either
if (coarsen_count < (refine_count - successful_refine_count))
coarsen_count = 0;
else
coarsen_count -= (refine_count - successful_refine_count);
if (coarsen_count > max_elem_coarsen)
coarsen_count = max_elem_coarsen;
unsigned int successful_coarsen_count = 0;
if (coarsen_count)
{
for (unsigned int i=0; i != sorted_parent_error.size(); ++i)
{
if (successful_coarsen_count >= coarsen_count * twotodim)
break;
unsigned int parent_id = sorted_parent_error[i].second;
Elem *parent = _mesh.query_elem(parent_id);
// On a ParallelMesh we skip remote elements
if (!parent)
continue;
libmesh_assert(parent->has_children());
for (unsigned int c=0; c != parent->n_children(); ++c)
{
Elem *elem = parent->child(c);
if (elem && elem != remote_elem)
{
libmesh_assert(elem->active());
elem->set_refinement_flag(Elem::COARSEN);
successful_coarsen_count++;
}
}
}
}
// Return true if we've done all the AMR/C we can
if (!successful_coarsen_count &&
!successful_refine_count)
return true;
// And false if there may still be more to do.
return false;
}
