graph_utils.hh

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#ifndef UTOPIA_DATAIO_GRAPH_UTILS_HH
#define UTOPIA_DATAIO_GRAPH_UTILS_HH
 
#include <tuple>
 
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/adjacency_matrix.hpp>
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/properties.hpp>
#include <boost/hana/all_of.hpp>
#include <boost/hana/ext/std/tuple.hpp>
#include <boost/hana/for_each.hpp>
 
#include <hdf5.h>
 
#include "../core/logging.hh"
#include "../core/type_traits.hh"
#include "../core/graph/iterator.hh"
#include "hdfdataset.hh"
#include "hdfgroup.hh"
 
using namespace std::literals::string_literals;
 
namespace Utopia {
namespace DataIO {
namespace GraphUtilsHelper{
 
template <typename Graph>
std::pair<std::shared_ptr<HDFDataset>,
          std::shared_ptr<HDFDataset>>
setup_graph_containers(const Graph& g, const std::shared_ptr<HDFGroup>& grp)
{
    // Collect some information on the graph
    const auto num_vertices = boost::num_vertices(g);
    const auto num_edges    = boost::num_edges(g);
 
    // Get a logger to use here (Note: needs to have been setup beforehand)
    spdlog::get("data_io")->info("Saving graph with {} vertices and {} edges "
                                 "...", num_vertices, num_edges);
 
    // Initialize datasets to store vertices and edges in
    auto dset_vertices = grp->open_dataset("_vertices", { num_vertices });
    auto dset_edges = grp->open_dataset("_edges", { 2, num_edges });
    // NOTE Need shape to be {2, num_edges} because `write` writes line by line.
 
    // Set attributes
    dset_vertices->add_attribute("dim_name__0", "vertex_idx");
    dset_vertices->add_attribute("coords_mode__vertex_idx", "trivial");
 
    dset_edges->add_attribute("dim_name__0", "label");
    dset_edges->add_attribute("coords_mode__label", "values");
    dset_edges->add_attribute("coords__label",
                              std::vector<std::string>{"source", "target"});
    dset_edges->add_attribute("dim_name__1", "edge_idx");
    dset_edges->add_attribute("coords_mode__edge_idx", "trivial");
 
    return std::make_pair(dset_vertices, dset_edges);
}
 
template <typename First, typename Second, typename... Tail>
constexpr std::tuple<Tail...> tuple_tail(const std::tuple<First, Second,
                                                          Tail...>& t)
{
    return std::apply([](auto, auto, auto... tail) {
        return std::make_tuple(tail...);}, t);
}
 
template <typename CoordT>
auto coords_container()
{
    if constexpr (Utils::is_string_v<CoordT>) {
        return std::vector<std::string>{};
    }
    else {
        return std::vector<CoordT>{};
    } 
}
 
enum class EntityKind {
    vertex,
    edge
};
 
template <EntityKind entity_kind,
          typename Graph,
          typename NWGroup,
          typename ItPair>
auto generate_write_function(const Graph& g,
                             NWGroup&& nw_grp,
                             std::string label,
                             ItPair&& it_pair,
                             std::size_t num_entities)
{
    static_assert(entity_kind == EntityKind::vertex or
                  entity_kind == EntityKind::edge,
                  "Error, 'entity_kind' has to be either 'vertex' or 'edge'");
 
    return
        [&g,
         nw_grp{std::forward<NWGroup>(nw_grp)},
         label{std::move(label)},
         it_pair{std::forward<ItPair>(it_pair)},
         num_entities{std::move(num_entities)}] (auto&& write_spec)
        // By-reference captures are used where possible to avoid additional
        // copies. Note that this is not possible for label and num_entities.
        {
 
        std::string prop_prefix;
 
        if constexpr (entity_kind == EntityKind::vertex) {
            prop_prefix = "vertex";
        }
        else {
            prop_prefix = "edge";
        }
 
        const auto grp =
            nw_grp->open_group(std::get<0>(write_spec));
 
        // ... 1D case if second element of write_spec is a callable object
        //     such that the write specifications are of the form
        //     write_spec = (std::string name_adaptor, lambda adaptor)
        if constexpr (Utils::is_callable_v<std::tuple_element_t<1, 
                                    std::decay_t<decltype(write_spec)>>>)
        {
            const auto dset = grp->open_dataset(label, { num_entities });
 
            dset->write(it_pair.first, it_pair.second,
                [&](auto&& desc) {
                    return std::get<1>(write_spec)(desc, g);
                }
            );
 
            dset->add_attribute("dim_name__0", prop_prefix + "_idx");
            dset->add_attribute("coords_mode__"s + prop_prefix + "_idx",
                                "trivial");
        }
 
        // ... 2D case otherwise
        //     write_spec = (adaptor_name, dim0_name,
        //                        (coord1, adaptor1),
        //                        (coord2, adaptor2), ...)
        else {
 
            static_assert(Utils::is_string_v<std::tuple_element_t<1,
                                    std::decay_t<decltype(write_spec)>>>,
                          "Error, the name of dimension 0 has to be s string");
 
            // Extract the adaptor pairs (coord, adaptor) from write_spec tuple
            const auto adaptor_pairs = tuple_tail(write_spec);
            // FIXME This cannot be calculated at compile time since
            //       hana::for_each uses non-constexpr access.
 
            // Get number of adaptors
            constexpr auto num_adaptors = std::tuple_size_v<std::decay_t<
                                                    decltype(adaptor_pairs)>>;
 
            // Open a 2D dataset
            const auto dset = grp->open_dataset(label,
                                                {num_adaptors, num_entities});
 
            // Deduce coordinate container type from adaptor_pairs
            using WriteSpecT = std::decay_t<decltype(write_spec)>;
            using FirstTupElementT = std::tuple_element_t<2, WriteSpecT>;
            using CoordT = std::tuple_element_t<0, FirstTupElementT>;
 
            // Create the (empty) coordinates container
            auto coords = coords_container<CoordT>();
 
            // Create the lambda that saves the data to the captured
            // fire-and-forget dataset and stores the coordinate value
            auto apply_adaptor = [&](auto&& adaptor_pair){
                // adaptor_pair = (coordinate, adaptor_function)
                dset->write(it_pair.first, it_pair.second,
                    [&](auto&& desc) {
                        return std::get<1>(adaptor_pair)(desc, g);
                    }
                );
 
                static_assert(
                    // assert matching coordinate types
                    std::is_same_v<
                            std::tuple_element_t<0,
                                    std::decay_t<decltype(adaptor_pair)>>,
                            CoordT>,
                    "Error, coordinate types do not match! Check that all "
                    "coordinates are of the same type");
 
                coords.push_back(std::get<0>(adaptor_pair));
            };
 
            boost::hana::for_each(adaptor_pairs, apply_adaptor);
 
            // Extract the 0th dimension name from the write spec
            const std::string dim0_name = std::get<1>(write_spec);
 
            // Set attributes
            dset->add_attribute("dim_name__0", dim0_name);
            dset->add_attribute("coords_mode__"s + dim0_name, "values");
            dset->add_attribute("coords__"s + dim0_name, coords);
 
            dset->add_attribute("dim_name__1", prop_prefix + "_idx");
            dset->add_attribute("coords_mode__"s + prop_prefix + "_idx",
                                "trivial");
        }
    };
}
 
} // namespace GraphUtilsHelper
 
template <typename Graph>
std::shared_ptr<HDFGroup>
create_graph_group(const Graph&                       g,
                   const std::shared_ptr<HDFGroup>&   parent_grp,
                   const std::string&                 name)
{
    // Create the group for the graph and store metadata in its attributes
    auto grp = parent_grp->open_group(name);
 
    grp->add_attribute("content", "graph");
    // Store additional metadata in the group attributes
    grp->add_attribute("is_directed", boost::is_directed(g));
    grp->add_attribute("allows_parallel", boost::allows_parallel_edges(g));
 
    // Store the information on the edge container shape
    // NOTE Here, it is assumed that the edge data is written in shape (2,N).
    //      If this is not the case, the attribute must be overwritten.
    grp->add_attribute("edge_container_is_transposed", true);
 
    // Prevent the vertex and edge dimension from being squeezed when selecting
    // graph data via the GraphGroup.
    grp->add_attribute(
        "keep_dim", std::vector<std::string>{"vertex_idx", "edge_idx"}
    );
 
    spdlog::get("data_io")->info("Opened graph group '{}'.", name);
 
    return grp;
}
 
 
template <typename Graph>
void
save_graph(const Graph& g, const std::shared_ptr<HDFGroup>& grp)
{
    // Create and prepare the datasets for vertices and edges
    auto [dset_vertices,
          dset_edges] = GraphUtilsHelper::setup_graph_containers(g, grp);
 
    // Save vertex list
    auto [v, v_end] = boost::vertices(g);
    dset_vertices->write(v, v_end, [&](auto vd) {
        return boost::get(boost::vertex_index_t(), g, vd);
    });
 
    // Save edges
    // NOTE Need to call write twice to achieve the desired data shape.
    auto [e, e_end] = boost::edges(g);
    dset_edges->write(e, e_end, [&](auto ed) {
        return boost::get(boost::vertex_index_t(), g, boost::source(ed, g));
    });
 
    dset_edges->write(e, e_end, [&](auto ed) {
        return boost::get(boost::vertex_index_t(), g, boost::target(ed, g));
    });
 
    spdlog::get("data_io")->debug("Graph saved.");
}
 
 
template <typename Graph, typename PropertyMap>
void
save_graph(const Graph&                       g,
           const std::shared_ptr<HDFGroup>&   grp,
           const PropertyMap                  vertex_ids)
{
    // Create and prepare the datasets for vertices and edges
    auto [dset_vertices,
          dset_edges] = GraphUtilsHelper::setup_graph_containers(g, grp);
 
    // Save vertex list
    auto [v, v_end] = boost::vertices(g);
    dset_vertices->write(
        v, v_end, [&](auto vd) { return boost::get(vertex_ids, vd); });
 
    // Save edges
    // NOTE Need to call write twice to achieve the desired data shape.
    auto [e, e_end] = boost::edges(g);
    dset_edges->write(e, e_end, [&](auto ed) {
        return boost::get(vertex_ids, boost::source(ed, g));
    });
 
    dset_edges->write(e, e_end, [&](auto ed) {
        return boost::get(vertex_ids, boost::target(ed, g));
    });
 
    spdlog::get("data_io")->debug("Graph saved.");
}
 
template <IterateOver iterate_over, typename Graph, typename... Adaptors>
void
save_graph_entity_properties(const Graph&                       g,
                             const std::shared_ptr<HDFGroup>&   nw_grp,
                             const std::string&                 label,
                             const std::tuple<Adaptors...>&     adaptor_tuple)
{
 
    static_assert(
        // assert stringlike-ness of first thing
        std::conjunction_v<Utils::is_string<
            std::tuple_element_t<0, std::decay_t<Adaptors>>>...>,
        "Error, the first entry of each entry of 'adaptor_tuple' has to be "
        "string like, to name the adaptor");
 
    static_assert(
        iterate_over == IterateOver::vertices or
        iterate_over == IterateOver::edges, "Error, unknown iterator type! "
        "Has to be either 'IterateOver::vertices' or 'IterateOver::edges'"
    );
 
    // NOTE Consider a check for literal types, which is more capable than
    //      the (now removed) std::is_literal_type ...
 
    // Get a logger
    auto log = spdlog::get("data_io");
 
    using GraphUtilsHelper::EntityKind;
    using GraphUtilsHelper::generate_write_function;
 
    // ... vertex_iterator ...
    if constexpr (iterate_over == IterateOver::vertices)
    {
        // Collect some information on the graph
        const auto num_vertices = boost::num_vertices(g);
 
        // Make vertex iterator pair
        auto it_pair = GraphUtils::iterator_pair<IterateOver::vertices>(g);
 
        // Get write function that saves data given by the adaptor(s) to new
        // dataset(s), fire-and-forget
        auto write_f = generate_write_function<EntityKind::vertex>(
                                                        g, nw_grp,
                                                        label,
                                                        it_pair,
                                                        num_vertices);
 
        boost::hana::for_each(adaptor_tuple, write_f);
 
        log->debug("Graph vertex properties saved with label '{}'.", label);
    }
 
    // ... and edge_iterator
    else {
        // Collect some information on the graph
        const auto num_edges = boost::num_edges(g);
 
        // Make edge iterator pair
        auto it_pair = GraphUtils::iterator_pair<IterateOver::edges>(g);
 
        // Get write function that saves data given by the adaptor(s) to new
        // dataset(s), fire-and-forget
        auto write_f = generate_write_function<EntityKind::edge>(
                                                        g, nw_grp,
                                                        label,
                                                        it_pair,
                                                        num_edges);
 
        boost::hana::for_each(adaptor_tuple, write_f);
 
        log->debug("Graph edge properties saved with label '{}'.", label);
    }
}
 
template <typename Graph, typename... Adaptors>
void
save_vertex_properties(Graph&&                            g,
                       const std::shared_ptr<HDFGroup>&   nw_grp,
                       const std::string&                 label,
                       const std::tuple<Adaptors...>&     adaptor_tuple)
{
    save_graph_entity_properties<IterateOver::vertices>(std::forward<Graph>(g),
                                                        nw_grp,
                                                        label,
                                                        adaptor_tuple);
}
 
template <typename Graph, typename... Adaptors>
void
save_edge_properties(Graph&&                            g,
                     const std::shared_ptr<HDFGroup>&   nw_grp,
                     const std::string&                 label,
                     const std::tuple<Adaptors...>&     adaptor_tuple)
{
    save_graph_entity_properties<IterateOver::edges>(std::forward<Graph>(g),
                                                     nw_grp,
                                                     label,
                                                     adaptor_tuple);
}
 
// TODO add functions here to open datasets for edge or vertex attributes.
 // end of group GraphUtilities // end of group DataIO
 
} // namespace DataIO
} // namespace Utopia
 
#endif // UTOPIA_DATAIO_GRAPH_UTILS_HH