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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "hnsw_index_saver.h"
#include "hnsw_graph.h"
#include <vespa/searchlib/util/bufferwriter.h>
#include <limits>
#include <cassert>
namespace search::tensor {
namespace {
template <HnswIndexType type>
size_t
count_valid_link_arrays(const HnswGraph<type> & graph) {
size_t count(0);
size_t num_nodes = graph.nodes.get_size(); // Called from writer only
for (size_t i = 0; i < num_nodes; ++i) {
auto levels_ref = graph.get_levels_ref(i);
if (levels_ref.valid()) {
count += graph.levels_store.get(levels_ref).size();
}
}
return count;
}
}
template <HnswIndexType type>
HnswIndexSaver<type>::MetaData::MetaData()
: entry_nodeid(0),
entry_level(-1),
refs(),
nodes()
{}
template <HnswIndexType type>
HnswIndexSaver<type>::MetaData::~MetaData() = default;
template <HnswIndexType type>
HnswIndexSaver<type>::~HnswIndexSaver() = default;
template <HnswIndexType type>
HnswIndexSaver<type>::HnswIndexSaver(const HnswGraph<type> &graph)
: _graph_links(graph.links_store), _meta_data()
{
auto entry = graph.get_entry_node();
_meta_data.entry_nodeid = entry.nodeid;
_meta_data.entry_level = entry.level;
size_t num_nodes = graph.nodes.get_size(); // Called from writer only
assert (num_nodes <= (std::numeric_limits<uint32_t>::max() - 1));
size_t link_array_count = count_valid_link_arrays(graph);
assert (link_array_count <= std::numeric_limits<uint32_t>::max());
_meta_data.refs.reserve(link_array_count);
_meta_data.nodes.reserve(num_nodes+1);
for (size_t i = 0; i < num_nodes; ++i) {
auto& node = graph.nodes.get_elem_ref(i);
_meta_data.nodes.emplace_back(_meta_data.refs.size(), node);
auto levels_ref = node.levels_ref().load_relaxed();
if (levels_ref.valid()) {
auto levels = graph.levels_store.get(levels_ref);
for (const auto& links_ref : levels) {
_meta_data.refs.push_back(links_ref.load_relaxed());
}
}
}
_meta_data.nodes.emplace_back(_meta_data.refs.size());
}
template <HnswIndexType type>
void
HnswIndexSaver<type>::save(BufferWriter& writer) const
{
writer.write(&_meta_data.entry_nodeid, sizeof(uint32_t));
writer.write(&_meta_data.entry_level, sizeof(int32_t));
uint32_t num_nodes = _meta_data.nodes.size() - 1;
writer.write(&num_nodes, sizeof(uint32_t));
for (uint32_t i(0); i < num_nodes; i++) {
auto& node = _meta_data.nodes[i];
uint32_t offset = node.get_refs_offset();
uint32_t next_offset = _meta_data.nodes[i+1].get_refs_offset();
uint32_t num_levels = next_offset - offset;
writer.write(&num_levels, sizeof(uint32_t));
if (num_levels > 0) {
if constexpr (!HnswIndexSaverMetaDataNode<type>::identity_mapping) {
uint32_t docid = node.get_docid();
uint32_t subspace = node.get_subspace();
writer.write(&docid, sizeof(uint32_t));
writer.write(&subspace, sizeof(uint32_t));
}
}
for (; offset < next_offset; offset++) {
auto links_ref = _meta_data.refs[offset];
if (links_ref.valid()) {
vespalib::ConstArrayRef<uint32_t> link_array = _graph_links.get(links_ref);
uint32_t num_links = link_array.size();
writer.write(&num_links, sizeof(uint32_t));
writer.write(link_array.cbegin(), sizeof(uint32_t)*num_links);
} else {
uint32_t num_links = 0;
writer.write(&num_links, sizeof(uint32_t));
}
}
}
writer.flush();
}
template class HnswIndexSaver<HnswIndexType::SINGLE>;
template class HnswIndexSaver<HnswIndexType::MULTI>;
}
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