Hi, everyone
I’m not familiar to ASPECT, could someone tell me how to get the data of
ghost cells?
In the ASPECT, I find that it is implemented through the following
functions to obtain ghost particles
in ~/aspect/source/particle/world.cc
template <int dim>
std::map<types::subdomain_id,unsigned int>
World<dim>::get_subdomain_id_to_neighbor_map() const
{
}
template <int dim>
void
World<dim>::exchange_ghost_particles()
{
}
template <int dim>
void
World<dim>::send_recv_particles
(const std::vector<std::vector<std::pair<types::LevelInd,Particle <dim> > >
> &send_particles,
std::vector<std::pair<types::LevelInd,
Particle<dim> > > &received_particles)
{
}
*Presently, I just have a simple data(for example, an object of
vector<valuetype> on each cell), which is not so complex like the particle,
how can I realize this this easily?*
Thanks very much!
May modify directly in the following codes
template <int dim>
std::map<types::subdomain_id, unsigned int>
World<dim>::get_subdomain_id_to_neighbor_map() const
{
std::map<types::subdomain_id, unsigned int>
subdomain_id_to_neighbor_map;
const std::set<types::subdomain_id> ghost_owners =
this->get_triangulation().ghost_owners();
std::set<types::subdomain_id>::const_iterator ghost_owner =
ghost_owners.begin();
for (unsigned int neighbor_id=0; neighbor_id<ghost_owners.size();
++neighbor_id,++ghost_owner)
{
subdomain_id_to_neighbor_map.insert(std::make_pair(*ghost_owner,neighbor_id));
}
return subdomain_id_to_neighbor_map;
}
template <int dim>
void
World<dim>::exchange_ghost_particles()
{
TimerOutput::Scope timer_section(this->get_computing_timer(),
"Particles: Exchange ghosts");
// First clear the current ghost_particle information
ghost_particles.clear();
const std::map<types::subdomain_id, unsigned int>
subdomain_to_neighbor_map(get_subdomain_id_to_neighbor_map());
std::vector<std::vector<std::pair<types::LevelInd, Particle<dim> > >
> ghost_particles_by_domain(subdomain_to_neighbor_map.size());
std::vector<std::set<unsigned int> >
vertex_to_neighbor_subdomain(this->get_triangulation().n_vertices());
typename DoFHandler<dim>::active_cell_iterator
cell = this->get_dof_handler().begin_active(),
endc = this->get_dof_handler().end();
for (; cell != endc; ++cell)
{
if (cell->is_ghost())
for (unsigned int v=0; v<GeometryInfo<dim>::vertices_per_cell;
++v)
vertex_to_neighbor_subdomain[cell->vertex_index(v)].insert(cell->subdomain_id());
}
cell = this->get_triangulation().begin_active();
for (; cell != endc; ++cell)
{
if (!cell->is_ghost())
{
std::set<unsigned int> cell_to_neighbor_subdomain;
for (unsigned int v=0;
v<GeometryInfo<dim>::vertices_per_cell; ++v)
{
cell_to_neighbor_subdomain.insert(vertex_to_neighbor_subdomain[cell->vertex_index(v)].begin(),
vertex_to_neighbor_subdomain[cell->vertex_index(v)].end());
}
if (cell_to_neighbor_subdomain.size() > 0)
{
const std::pair< const typename
std::multimap<types::LevelInd,Particle <dim> >::iterator,
const typename
std::multimap<types::LevelInd,Particle <dim> >::iterator>
particle_range_in_cell =
particles.equal_range(std::make_pair(cell->level(),cell->index()));
for (std::set<types::subdomain_id>::const_iterator
domain=cell_to_neighbor_subdomain.begin();
domain != cell_to_neighbor_subdomain.end(); ++domain)
{
const unsigned int neighbor_id =
subdomain_to_neighbor_map.find(*domain)->second;
ghost_particles_by_domain[neighbor_id].insert(
ghost_particles_by_domain[neighbor_id].end(),
particle_range_in_cell.first,
particle_range_in_cell.second);
}
}
}
}
std::vector<std::pair<types::LevelInd, Particle<dim> > >
received_ghost_particles;
send_recv_particles(ghost_particles_by_domain,
received_ghost_particles);
ghost_particles.insert(received_ghost_particles.begin(),
received_ghost_particles.end());
}
*I'm not clear about the particles.equal_range().*
*The following send_receive particles is mots difficult for me to
understand*
template <int dim>
void
World<dim>::send_recv_particles(const
std::vector<std::vector<std::pair<types::LevelInd,Particle <dim> > > >
&send_particles,
std::vector<std::pair<types::LevelInd,
Particle<dim> > > &received_particles)
{
// Determine the communication pattern
const std::vector<types::subdomain_id> neighbors
(this->get_triangulation().ghost_owners().begin(),
this->get_triangulation().ghost_owners().end());
const unsigned int n_neighbors = neighbors.size();
Assert(n_neighbors == send_particles.size(),
ExcMessage("The particles to send to other processes should be
sorted into a vector "
"containing as many vectors of particles as there
are neighbor processes. This "
"is not the case for an unknown reason. Contact the
developers if you encounter "
"this error."));
unsigned int n_send_particles = 0;
for (unsigned int i=0; i<n_neighbors; ++i)
n_send_particles += send_particles[i].size();
#if DEAL_II_VERSION_GTE(8,5,0)
const unsigned int cellid_size = sizeof(CellId::binary_type);
const unsigned int particle_size =
property_manager->get_particle_size() + integrator->get_data_size() +
cellid_size;
#else
const unsigned int particle_size =
property_manager->get_particle_size() + integrator->get_data_size();
#endif
// Determine the amount of data we will send to other processors
std::vector<unsigned int> n_send_data(n_neighbors);
std::vector<unsigned int> n_recv_data(n_neighbors);
std::vector<unsigned int> send_offsets(n_neighbors);
std::vector<unsigned int> recv_offsets(n_neighbors);
// Allocate space for sending and receiving particle data
std::vector<char> send_data(n_send_particles * particle_size);
void *data = static_cast<void *> (&send_data.front());
for (types::subdomain_id neighbor_id = 0; neighbor_id < n_neighbors;
++neighbor_id)
{
send_offsets[neighbor_id] = reinterpret_cast<std::size_t> (data)
- reinterpret_cast<std::size_t> (&send_data.front());
// Copy the particle data into the send array
typename std::vector<std::pair<types::LevelInd,Particle <dim> >
>::const_iterator
cell_particle = send_particles[neighbor_id].begin(),
end_particle = send_particles[neighbor_id].end();
for (; cell_particle != end_particle; ++cell_particle)
{
#if DEAL_II_VERSION_GTE(8,5,0)
const typename
parallel::distributed::Triangulation<dim>::cell_iterator cell
(&this->get_triangulation(),
cell_particle->first.first,
cell_particle->first.second);
const CellId::binary_type cellid = cell->id().template
to_binary<dim>();
memcpy(data, &cellid, cellid_size);
data = static_cast<char *>(data) + cellid_size;
#endif
cell_particle->second.write_data(data);
data = integrator->write_data(data,
cell_particle->second.get_id());
}
n_send_data[neighbor_id] = reinterpret_cast<std::size_t> (data) -
send_offsets[neighbor_id] - reinterpret_cast<std::size_t>
(&send_data.front());
}
// Notify other processors how many particles we will send
std::vector<MPI_Request> n_requests(2*n_neighbors);
for (unsigned int i=0; i<n_neighbors; ++i)
MPI_Irecv(&(n_recv_data[i]), 1, MPI_INT, neighbors[i], 0,
this->get_mpi_communicator(), &(n_requests[2*i]));
for (unsigned int i=0; i<n_neighbors; ++i)
MPI_Isend(&(n_send_data[i]), 1, MPI_INT, neighbors[i], 0,
this->get_mpi_communicator(), &(n_requests[2*i+1]));
MPI_Waitall(2*n_neighbors,&n_requests[0],MPI_STATUSES_IGNORE);
// Determine how many particles and data we will receive
unsigned int total_recv_data = 0;
for (unsigned int neighbor_id=0; neighbor_id<n_neighbors;
++neighbor_id)
{
recv_offsets[neighbor_id] = total_recv_data;
total_recv_data += n_recv_data[neighbor_id];
}
// Set up the space for the received particle data
std::vector<char> recv_data(total_recv_data);
// Exchange the particle data between domains
std::vector<MPI_Request> requests(2*n_neighbors);
unsigned int send_ops = 0;
unsigned int recv_ops = 0;
for (unsigned int i=0; i<n_neighbors; ++i)
if (n_recv_data[i] > 0)
{
MPI_Irecv(&(recv_data[recv_offsets[i]]), n_recv_data[i],
MPI_CHAR, neighbors[i], 1,
this->get_mpi_communicator(),&(requests[send_ops]));
send_ops++;
}
for (unsigned int i=0; i<n_neighbors; ++i)
if (n_send_data[i] > 0)
{
MPI_Isend(&(send_data[send_offsets[i]]), n_send_data[i],
MPI_CHAR, neighbors[i], 1,
this->get_mpi_communicator(),&(requests[send_ops+recv_ops]));
recv_ops++;
}
MPI_Waitall(send_ops+recv_ops,&requests[0],MPI_STATUSES_IGNORE);
// Put the received particles into the domain if they are in the
triangulation
const void *recv_data_it = static_cast<const void *>
(&recv_data.front());
#if !DEAL_II_VERSION_GTE(8,5,0)
const std::vector<std::set<typename
Triangulation<dim>::active_cell_iterator> >
vertex_to_cells(GridTools::vertex_to_cell_map(this->get_triangulation()));
const std::vector<std::vector<Tensor<1,dim> > >
vertex_to_cell_centers(vertex_to_cell_centers_directions(vertex_to_cells));
std::vector<unsigned int> neighbor_permutation;
#endif
while (reinterpret_cast<std::size_t> (recv_data_it) -
reinterpret_cast<std::size_t> (&recv_data.front()) < total_recv_data)
{
#if DEAL_II_VERSION_GTE(8,5,0)
CellId::binary_type binary_cellid;
memcpy(&binary_cellid, recv_data_it, cellid_size);
const CellId id(binary_cellid);
recv_data_it = static_cast<const char *> (recv_data_it) +
cellid_size;
const typename
parallel::distributed::Triangulation<dim>::active_cell_iterator cell =
id.to_cell(this->get_triangulation());
const Particle<dim>
recv_particle(recv_data_it,property_manager->get_particle_size());
recv_data_it = integrator->read_data(recv_data_it,
recv_particle.get_id());
#else
Particle<dim>
recv_particle(recv_data_it,property_manager->get_particle_size());
recv_data_it = integrator->read_data(recv_data_it,
recv_particle.get_id());
const std::pair<const typename
parallel::distributed::Triangulation<dim>::active_cell_iterator,
Point<dim> > current_cell_and_position =
GridTools::find_active_cell_around_point<>
(this->get_mapping(),
this->get_triangulation(),
recv_particle.get_location());
typename
parallel::distributed::Triangulation<dim>::active_cell_iterator cell =
current_cell_and_position.first;
recv_particle.set_reference_location(current_cell_and_position.second);
// GridTools::find_active_cell_around_point can find a different
cell than
// particle_is_in_cell if the particle is very close to the
boundary
// therefore, we might get a cell here that does not belong to us.
// But then at least one of its neighbors belongs to us, and the
particle
// is extremely close to the boundary of these two cells. Look in
the
// neighbor cells for the particle.
if (!cell->is_locally_owned())
{
const unsigned int closest_vertex =
get_closest_vertex_of_cell(cell,recv_particle.get_location());
const unsigned int closest_vertex_index =
cell->vertex_index(closest_vertex);
Tensor<1,dim> vertex_to_particle =
recv_particle.get_location() - cell->vertex(closest_vertex);
vertex_to_particle /= vertex_to_particle.norm();
const unsigned int n_neighbor_cells =
vertex_to_cells[closest_vertex_index].size();
neighbor_permutation.resize(n_neighbor_cells);
for (unsigned int i=0; i<n_neighbor_cells; ++i)
neighbor_permutation[i] = i;
std::sort(neighbor_permutation.begin(),
neighbor_permutation.end(),
std_cxx11::bind(&compare_particle_association<dim>,
std_cxx11::_1,
std_cxx11::_2,
std_cxx11::cref(vertex_to_particle),
std_cxx11::cref(vertex_to_cell_centers[closest_vertex_index])));
// Search all of the cells adjacent to the closest vertex of
the previous cell
// Most likely we will find the particle in them.
for (unsigned int i=0; i<n_neighbor_cells; ++i)
{
try
{
typename std::set<typename
Triangulation<dim>::active_cell_iterator>::const_iterator neighbor_cell =
vertex_to_cells[closest_vertex_index].begin();
std::advance(neighbor_cell,neighbor_permutation[i]);
const Point<dim> p_unit =
this->get_mapping().transform_real_to_unit_cell(*neighbor_cell,
recv_particle.get_location());
if (GeometryInfo<dim>::is_inside_unit_cell(p_unit))
{
cell = *neighbor_cell;
recv_particle.set_reference_location(p_unit);
break;
}
}
catch (typename Mapping<dim>::ExcTransformationFailed &)
{}
}
}
#endif
const types::LevelInd found_cell =
std::make_pair(cell->level(),cell->index());
received_particles.push_back(std::make_pair(found_cell,
recv_particle));
}
AssertThrow(recv_data_it == &recv_data.back()+1,
ExcMessage("The amount of data that was read into new
particles "
"does not match the amount of data sent
around."));
}
Thanks so much!
Best
Jack
>
> Just for reference, Rene Gassmoeller implemented something similar for
> particles recently: There, we store particles on every locally owned cell,
> but
> there are times when one also wants to access particles on ghost cells.
> This
> is implemented here:
> https://github.com/geodynamics/aspect/pull/1216
> https://github.com/geodynamics/aspect/pull/1253
>
> It's not terribly complicated because one just has to gather the
> information
> on cells that are ghosts on some other processor, and then send this
> information to all relevant processors.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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