grid_synchronizer.cc
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Created: Wed, Dec 4, 18:48

grid_synchronizer.cc
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	/**
	* Copyright (©) 2011-2023 EPFL (Ecole Polytechnique Fédérale de Lausanne)
	* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
	*
	* This file is part of Akantu
	*
	* Akantu is free software: you can redistribute it and/or modify it under the
	* terms of the GNU Lesser General Public License as published by the Free
	* Software Foundation, either version 3 of the License, or (at your option) any
	* later version.
	*
	* Akantu is distributed in the hope that it will be useful, but WITHOUT ANY
	* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
	* A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
	* details.
	*
	* You should have received a copy of the GNU Lesser General Public License
	* along with Akantu. If not, see <http://www.gnu.org/licenses/>.
	*/

	/* -------------------------------------------------------------------------- */
	#include "grid_synchronizer.hh"
	#include "aka_grid_dynamic.hh"
	#include "communicator.hh"
	#include "fe_engine.hh"
	#include "integration_point.hh"
	#include "mesh.hh"
	#include "mesh_io.hh"
	#include <iostream>

	/* -------------------------------------------------------------------------- */

	namespace akantu {

	/* -------------------------------------------------------------------------- */
	template <class E>
	void GridSynchronizer::createGridSynchronizer(const SpatialGrid<E> & grid) {
	AKANTU_DEBUG_IN();

	const auto & comm = this->mesh.getCommunicator();
	auto nb_proc = comm.getNbProc();
	auto my_rank = comm.whoAmI();

	if (nb_proc == 1) {
	return;
	}

	auto spatial_dimension = this->mesh.getSpatialDimension();

	BBox my_bounding_box(spatial_dimension);

	const auto & lower = grid.getLowerBounds();
	const auto & upper = grid.getUpperBounds();
	const auto & spacing = grid.getSpacing();

	my_bounding_box.setLowerBounds(lower - spacing);
	my_bounding_box.setUpperBounds(upper + spacing);

	AKANTU_DEBUG_INFO(
	"Exchange of bounding box to detect the overlapping regions.");

	auto && bboxes = my_bounding_box.allGather(comm);

	std::vector<bool> intersects_proc(nb_proc);
	std::fill(intersects_proc.begin(), intersects_proc.end(), true);

	Matrix<Int> first_cells(spatial_dimension, nb_proc);
	Matrix<Int> last_cells(spatial_dimension, nb_proc);

	std::map<Int, ElementTypeMapArray<Idx>> element_per_proc;

	// check the overlapping between my box and the one from other processors
	for (Int p = 0; p < nb_proc; ++p) {
	if (p == my_rank) {
	continue;
	}

	const auto & proc_bounding_box = bboxes[p];
	auto intersection = my_bounding_box.intersection(proc_bounding_box);

	auto && first_cell_p = first_cells(p);
	auto && last_cell_p = last_cells(p);

	intersects_proc[p] = intersection;

	if (intersects_proc[p]) {
	for (Int s = 0; s < spatial_dimension; ++s) {
	first_cell_p(s) = grid.getCellID(intersection.getLowerBounds()(s), s);
	last_cell_p(s) = grid.getCellID(intersection.getUpperBounds()(s), s);
	}
	}

	// create the list of cells in the overlapping
	using CellID = typename SpatialGrid<E>::CellID;

	std::vector<CellID> cell_ids;

	if (intersects_proc[p]) {
	AKANTU_DEBUG_INFO("I intersects with processor " << p);

	CellID cell_id(spatial_dimension);

	for (Int fd = first_cell_p(0); fd <= last_cell_p(0); ++fd) {
	cell_id.setID(0, fd);
	if (spatial_dimension == 1) {
	cell_ids.push_back(cell_id);
	} else {
	for (Int sd = first_cell_p(1); sd <= last_cell_p(1); ++sd) {
	cell_id.setID(1, sd);
	if (spatial_dimension == 2) {
	cell_ids.push_back(cell_id);
	} else {
	for (Int ld = first_cell_p(2); ld <= last_cell_p(2); ++ld) {
	cell_id.setID(2, ld);
	cell_ids.push_back(cell_id);
	}
	}
	}
	}
	}

	// get the list of elements in the cells of the overlapping
	std::set<Element> to_send;
	for (auto & cur_cell_id : cell_ids) {
	auto & cell = grid.getCell(cur_cell_id);
	for (auto & element : cell) {
	to_send.insert(element);
	}
	}

	AKANTU_DEBUG_INFO("I have prepared " << to_send.size()
	<< " elements to send to processor "
	<< p);
	auto & scheme = this->getCommunications().createSendScheme(p);

	element_per_proc.emplace(
	std::piecewise_construct, std::forward_as_tuple(p),
	std::forward_as_tuple(
	std::string("element_per_proc_" + std::to_string(p)), id));

	auto & elempproc = element_per_proc[p];

	for (auto elem : to_send) {
	auto type = elem.type;
	auto nb_nodes_per_element = mesh.getNbNodesPerElement(type);

	// /!\ this part must be slow due to the access in the
	// ElementTypeMapArray<Idx>
	if (not elempproc.exists(type, _not_ghost)) {
	elempproc.alloc(0, nb_nodes_per_element, type, _not_ghost);
	}

	Vector<Idx> global_connect(nb_nodes_per_element);
	auto && local_connect = mesh.getConnectivity(type).begin(
	nb_nodes_per_element)[elem.element];

	for (Int i = 0; i < nb_nodes_per_element; ++i) {
	global_connect(i) = mesh.getNodeGlobalId(local_connect(i));
	AKANTU_DEBUG_ASSERT(
	global_connect(i) < mesh.getNbGlobalNodes(),
	"This global node send in the connectivity does not seem correct "
	<< global_connect(i) << " corresponding to "
	<< local_connect(i) << " from element " << elem.element);
	}

	elempproc(type).push_back(global_connect);
	scheme.push_back(elem);
	}
	}
	}

	AKANTU_DEBUG_INFO("I have finished to compute intersection,"
	<< " no it's time to communicate with my neighbors");

	/**
	* Sending loop, sends the connectivity asynchronously to all concerned proc
	*/
	std::vector<CommunicationRequest> isend_requests;
	Array<Int> space(0, 2);
	space.reserve(nb_proc * Int(_max_element_type));

	for (Int p = 0; p < nb_proc; ++p) {
	if (p == my_rank) {
	continue;
	}

	if (not intersects_proc[p]) {
	continue;
	}

	auto & elempproc = element_per_proc[p];
	Int count = 0;

	for (auto type : elempproc.elementTypes(_all_dimensions, _not_ghost)) {
	const auto & conn = elempproc(type, _not_ghost);
	space.push_back(
	Vector<Int>{Int(type), conn.size() * conn.getNbComponent()});
	VectorProxy<Int> info(space.data() + 2 * (space.size() - 1), 2);

	AKANTU_DEBUG_INFO(
	"I have " << conn.size() << " elements of type " << type
	<< " to send to processor " << p << " (communication tag : "
	<< Tag::genTag(my_rank, count, DATA_TAG) << ")");

	isend_requests.push_back(
	comm.asyncSend(info, p, Tag::genTag(my_rank, count, SIZE_TAG)));

	if (info[1] != 0) {
	isend_requests.push_back(
	comm.asyncSend(conn, p, Tag::genTag(my_rank, count, DATA_TAG)));
	}

	++count;
	}

	space.push_back(Vector<Int>{Int(_not_defined), 0});
	VectorProxy<Int> info(space.data() + 2 * (space.size() - 1), 2);
	isend_requests.push_back(
	comm.asyncSend(info, p, Tag::genTag(my_rank, count, SIZE_TAG)));
	}

	/**
	* Receives the connectivity and store them in the ghosts elements
	*/
	MeshAccessor mesh_accessor(mesh);
	auto & global_nodes_ids = mesh_accessor.getNodesGlobalIds();
	auto & nodes_type = mesh_accessor.getNodesFlags();

	std::vector<CommunicationRequest> isend_nodes_requests;
	Vector<Int> nb_nodes_to_recv(nb_proc);

	Int nb_total_nodes_to_recv = 0;
	Int nb_current_nodes = global_nodes_ids.size();

	NewNodesEvent new_nodes;
	NewElementsEvent new_elements;

	std::map<Int, std::vector<Int>> ask_nodes_per_proc;

	for (Int p = 0; p < nb_proc; ++p) {
	nb_nodes_to_recv(p) = 0;
	if (p == my_rank) {
	continue;
	}

	if (!intersects_proc[p]) {
	continue;
	}

	auto & scheme = this->getCommunications().createRecvScheme(p);

	ask_nodes_per_proc.emplace(std::piecewise_construct,
	std::forward_as_tuple(p),
	std::forward_as_tuple(0));

	auto & ask_nodes = ask_nodes_per_proc[p];
	Int count = 0;

	auto type = _not_defined;
	do {
	Vector<Int> info(2);
	comm.receive(info, p, Tag::genTag(p, count, SIZE_TAG));

	type = (ElementType)info[0];

	if (type == _not_defined) {
	break;
	}

	auto nb_nodes_per_element = mesh.getNbNodesPerElement(type);
	auto nb_element = info[1] / nb_nodes_per_element;

	Array<Idx> tmp_conn(nb_element, nb_nodes_per_element);
	if (info[1] != 0) {
	comm.receive(tmp_conn, p, Tag::genTag(p, count, DATA_TAG));
	}
	AKANTU_DEBUG_INFO("I will receive "
	<< nb_element << " elements of type "
	<< ElementType(info[0]) << " from processor " << p
	<< " (communication tag : "
	<< Tag::genTag(p, count, DATA_TAG) << ")");

	auto & ghost_connectivity = mesh_accessor.getConnectivity(type, _ghost);
	auto & ghost_counter = mesh_accessor.getGhostsCounters(type, _ghost);

	auto nb_ghost_element = ghost_connectivity.size();
	Element element{type, 0, _ghost};

	Vector<Idx> conn(nb_nodes_per_element);
	for (Int el = 0; el < nb_element; ++el) {
	Int nb_node_to_ask_for_elem = 0;

	for (Int n = 0; n < nb_nodes_per_element; ++n) {
	auto gn = tmp_conn(el, n);
	auto ln = global_nodes_ids.find(gn);

	AKANTU_DEBUG_ASSERT(gn < mesh.getNbGlobalNodes(),
	"This global node seems not correct "
	<< gn << " from element " << el << " node "
	<< n);

	if (ln == -1) {
	global_nodes_ids.push_back(gn);
	nodes_type.push_back(NodeFlag::_pure_ghost); // pure ghost node
	ln = nb_current_nodes;

	new_nodes.getList().push_back(ln);
	++nb_current_nodes;
	ask_nodes.push_back(gn);
	++nb_node_to_ask_for_elem;
	}
	conn[n] = ln;
	}

	// all the nodes are already known locally, the element should
	// already exists
	Idx c = -1;
	if (nb_node_to_ask_for_elem == 0) {
	c = ghost_connectivity.find(conn);
	element.element = c;
	}

	if (c == -1) {
	element.element = nb_ghost_element;
	++nb_ghost_element;
	ghost_connectivity.push_back(conn);
	ghost_counter.push_back(1);
	new_elements.getList().push_back(element);
	} else {
	++ghost_counter(c);
	}

	scheme.push_back(element);
	}

	count++;
	} while (type != _not_defined);

	AKANTU_DEBUG_INFO("I have "
	<< ask_nodes.size()
	<< " missing nodes for elements coming from processor "
	<< p << " (communication tag : "
	<< Tag::genTag(my_rank, 0, ASK_NODES_TAG) << ")");

	ask_nodes.push_back(-1);

	isend_nodes_requests.push_back(
	comm.asyncSend(ask_nodes, p, Tag::genTag(my_rank, 0, ASK_NODES_TAG)));
	nb_nodes_to_recv(p) = ask_nodes.size() - 1;
	nb_total_nodes_to_recv += nb_nodes_to_recv(p);
	}

	Communicator::waitAll(isend_requests);
	Communicator::freeCommunicationRequest(isend_requests);

	/**
	* Sends requested nodes to proc
	*/
	auto & nodes = mesh_accessor.getNodes();
	auto nb_nodes = nodes.size();

	std::vector<CommunicationRequest> isend_coordinates_requests;
	std::map<Int, Array<Real>> nodes_to_send_per_proc;
	for (Int p = 0; p < nb_proc; ++p) {
	if (p == my_rank or not intersects_proc[p]) {
	continue;
	}

	Array<Int> asked_nodes;
	CommunicationStatus status;
	AKANTU_DEBUG_INFO("Waiting list of nodes to send to processor "
	<< p << "(communication tag : "
	<< Tag::genTag(p, 0, ASK_NODES_TAG) << ")");

	comm.probe<Int>(p, Tag::genTag(p, 0, ASK_NODES_TAG), status);
	Int nb_nodes_to_send = status.size();
	asked_nodes.resize(nb_nodes_to_send);

	AKANTU_DEBUG_INFO("I have " << nb_nodes_to_send - 1
	<< " nodes to send to processor " << p
	<< " (communication tag : "
	<< Tag::genTag(p, 0, ASK_NODES_TAG) << ")");

	AKANTU_DEBUG_INFO("Getting list of nodes to send to processor "
	<< p << " (communication tag : "
	<< Tag::genTag(p, 0, ASK_NODES_TAG) << ")");

	comm.receive(asked_nodes, p, Tag::genTag(p, 0, ASK_NODES_TAG));

	nb_nodes_to_send--;
	asked_nodes.resize(nb_nodes_to_send);

	nodes_to_send_per_proc.emplace(std::piecewise_construct,
	std::forward_as_tuple(p),
	std::forward_as_tuple(0, spatial_dimension));

	auto & nodes_to_send = nodes_to_send_per_proc[p];
	auto node_it = nodes.begin(spatial_dimension);

	for (Int n = 0; n < nb_nodes_to_send; ++n) {
	auto ln = global_nodes_ids.find(asked_nodes(n));
	AKANTU_DEBUG_ASSERT(ln != -1, "The node [" << asked_nodes(n)
	<< "] requested by proc " << p
	<< " was not found locally!");
	nodes_to_send.push_back(node_it[ln]);
	}

	if (nb_nodes_to_send != 0) {
	AKANTU_DEBUG_INFO("Sending the "
	<< nb_nodes_to_send << " nodes to processor " << p
	<< " (communication tag : "
	<< Tag::genTag(p, 0, SEND_NODES_TAG) << ")");

	isend_coordinates_requests.push_back(comm.asyncSend(
	nodes_to_send, p, Tag::genTag(my_rank, 0, SEND_NODES_TAG)));
	}
	#if not defined(AKANTU_NDEBUG)
	else {
	AKANTU_DEBUG_INFO("No nodes to send to processor " << p);
	}
	#endif
	}

	Communicator::waitAll(isend_nodes_requests);
	Communicator::freeCommunicationRequest(isend_nodes_requests);

	nodes.resize(nb_total_nodes_to_recv + nb_nodes);
	for (Int p = 0; p < nb_proc; ++p) {
	if ((p != my_rank) && (nb_nodes_to_recv(p) > 0)) {
	AKANTU_DEBUG_INFO("Receiving the "
	<< nb_nodes_to_recv(p) << " nodes from processor " << p
	<< " (communication tag : "
	<< Tag::genTag(p, 0, SEND_NODES_TAG) << ")");

	VectorProxy<Real> nodes_to_recv(nodes.data() +
	nb_nodes * spatial_dimension,
	nb_nodes_to_recv(p) * spatial_dimension);
	comm.receive(nodes_to_recv, p, Tag::genTag(p, 0, SEND_NODES_TAG));
	nb_nodes += nb_nodes_to_recv(p);
	}
	#if not defined(AKANTU_NDEBUG)
	else {
	if (p != my_rank) {
	AKANTU_DEBUG_INFO("No nodes to receive from processor " << p);
	}
	}
	#endif
	}

	Communicator::waitAll(isend_coordinates_requests);
	Communicator::freeCommunicationRequest(isend_coordinates_requests);

	mesh.sendEvent(new_nodes);
	mesh.sendEvent(new_elements);

	AKANTU_DEBUG_OUT();
	}

	/* -------------------------------------------------------------------------- */
	template void GridSynchronizer::createGridSynchronizer<IntegrationPoint>(
	const SpatialGrid<IntegrationPoint> & grid);

	template void GridSynchronizer::createGridSynchronizer<Element>(
	const SpatialGrid<Element> & grid);

	} // namespace akantu

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