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// Copyright (C) 2025 Garth N. Wells
//
// This file is part of DOLFINx (https://www.fenicsproject.org)
//
// SPDX-License-Identifier: LGPL-3.0-or-later
#include "utils.h"
#include <algorithm>
#include <dolfinx/common/MPI.h>
#include <format>
#include <sstream>
#include <vector>
using namespace dolfinx;
//-----------------------------------------------------------------------------
graph::AdjacencyList<std::tuple<int, std::size_t, std::int8_t>,
std::pair<std::int32_t, std::int32_t>>
graph::comm_graph(const common::IndexMap& map, int root)
{
MPI_Comm comm = map.comm();
std::span<const int> dest = map.dest();
int ierr;
// Graph edge out(dest) weights
const std::vector<std::int32_t> w_dest = map.weights_dest();
// Group ranks by type
const auto [local_dest, local_src] = map.rank_type(MPI_COMM_TYPE_SHARED);
// Get number of edges for each node (rank)
int num_edges_local = dest.size();
std::vector<int> num_edges_remote(dolfinx::MPI::size(comm));
ierr = MPI_Gather(&num_edges_local, 1, MPI_INT, num_edges_remote.data(), 1,
MPI_INT, root, comm);
dolfinx::MPI::check_error(comm, ierr);
// Compute displacements
std::vector<int> disp(num_edges_remote.size() + 1, 0);
std::partial_sum(num_edges_remote.begin(), num_edges_remote.end(),
std::next(disp.begin()));
dolfinx::MPI::check_error(comm, ierr);
// For each node (rank), get edge indices
std::vector<int> edges_remote(disp.back());
edges_remote.reserve(1);
ierr = MPI_Gatherv(dest.data(), dest.size(), MPI_INT, edges_remote.data(),
num_edges_remote.data(), disp.data(), MPI_INT, root, comm);
dolfinx::MPI::check_error(comm, ierr);
// For each edge, get edge weight
std::vector<std::int32_t> weights_remote(disp.back());
weights_remote.reserve(1);
ierr = MPI_Gatherv(w_dest.data(), w_dest.size(), MPI_INT32_T,
weights_remote.data(), num_edges_remote.data(),
disp.data(), MPI_INT32_T, root, comm);
dolfinx::MPI::check_error(comm, ierr);
// For node get local and ghost sizes
std::vector<std::pair<std::int32_t, std::int32_t>> sizes_remote;
{
std::vector<std::int32_t> sizes_local(dolfinx::MPI::size(comm));
std::int32_t size = map.size_local();
ierr = MPI_Gather(&size, 1, MPI_INT32_T, sizes_local.data(), 1, MPI_INT32_T,
root, comm);
dolfinx::MPI::check_error(comm, ierr);
std::vector<std::int32_t> sizes_ghost(dolfinx::MPI::size(comm));
std::int32_t num_ghosts = map.num_ghosts();
ierr = MPI_Gather(&num_ghosts, 1, MPI_INT32_T, sizes_ghost.data(), 1,
MPI_INT32_T, root, comm);
dolfinx::MPI::check_error(comm, ierr);
std::transform(sizes_local.begin(), sizes_local.end(), sizes_ghost.begin(),
std::back_inserter(sizes_remote),
[](auto x, auto y) { return std::pair(x, y); });
}
// For each edge, get its local/remote marker
std::vector<std::int8_t> markers;
for (auto r : dest)
{
auto it = std::ranges::lower_bound(local_dest, r);
if (it != local_dest.end() and *it == r)
markers.push_back(1);
else
markers.push_back(0);
}
std::vector<std::int8_t> markers_remote(disp.back());
ierr = MPI_Gatherv(markers.data(), markers.size(), MPI_INT8_T,
markers_remote.data(), num_edges_remote.data(),
disp.data(), MPI_INT8_T, root, comm);
dolfinx::MPI::check_error(comm, ierr);
std::vector<std::tuple<int, std::size_t, std::int8_t>> e_data;
for (std::size_t i = 0; i < edges_remote.size(); ++i)
e_data.emplace_back(edges_remote[i], weights_remote[i], markers_remote[i]);
return graph::AdjacencyList(std::move(e_data),
std::vector(disp.begin(), disp.end()),
std::move(sizes_remote));
}
//-----------------------------------------------------------------------------
std::string graph::comm_to_json(
const graph::AdjacencyList<std::tuple<int, std::size_t, std::int8_t>,
std::pair<std::int32_t, std::int32_t>>& g)
{
const std::vector<std::pair<std::int32_t, std::int32_t>>& node_weights
= g.node_data().value();
std::stringstream out;
out << std::format("{{\"directed\": true, \"multigraph\": false, \"graph\": "
"[], \"nodes\": [");
for (std::int32_t n = 0; n < g.num_nodes(); ++n)
{
// Note: it is helpful to order map keys alphabetically
out << std::format("{{\"num_ghosts\": {}, \"weight\": {}, \"id\": {}}}",
node_weights[n].second, node_weights[n].first, n);
if (n != g.num_nodes() - 1)
out << ", ";
}
out << "], ";
out << "\"adjacency\": [";
for (std::int32_t n = 0; n < g.num_nodes(); ++n)
{
out << "[";
auto links = g.links(n);
for (std::size_t edge = 0; edge < links.size(); ++edge)
{
auto [e, w, local] = links[edge];
out << std::format("{{\"local\": {}, \"weight\": {}, \"id\": {}}}", local,
w, e);
if (edge != links.size() - 1)
out << ", ";
}
out << "]";
if (n != g.num_nodes() - 1)
out << ", ";
}
out << "]}";
return out.str();
}
//-----------------------------------------------------------------------------
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