How Is HNSWPQ Implemented in Code?

[zzyuewo]

i am new to coding，In IndexHNSW.cpp, the storage is always IndexPQ or not?
in void IndexHNSW::add()
{ ....
storage->add(n, x);
....
}
will it use the add method in IndexFlatCodes? because i see there is no add() in indexPQ and IndexPQ : IndexFlatCodes

in void hnsw_add_vertices()
{ ....
std::unique_ptr dis(storage_distance_computer(index_hnsw.storage));
....
}
but i think that DistanceComputer doesnt work for PQ

Which method is actually used by HNSWPQ? For these functions,(add, storage_distance_computer, set_query, add_with_locks)
i want to know how faiss combined HNSW and PQ in code, but i am confused

[rafayaar]

@zzyuewo

• If IndexHNSW is combined with PQ, storage would typically be an instance of IndexPQ, which in turn inherits from IndexFlatCodes.
• The add() method in IndexHNSW would delegate the call to IndexPQ::add(), but since IndexPQ does not have its own add() method, it inherits the add() method from IndexFlatCodes.
  In this method, the vectors are PQ-encoded before being added to the index.

For the functions (add, storage_distance_computer, set_query, add_with_locks)

• add(): Adds PQ-encoded vectors to the HNSW graph.
• storage_distance_computer(): Returns a PQ-specific distance computer for searching.
• set_query(): Sets the query vector, likely compressed using PQ before searching.
• add_with_locks(): Adds vectors to the HNSW graph while ensuring thread safety, encoding them with PQ if used.

i am new to coding，In IndexHNSW.cpp, the storage is always IndexPQ or not? in void IndexHNSW::add() { .... storage->add(n, x); .... } will it use the add method in IndexFlatCodes? because i see there is no add() in indexPQ and IndexPQ : IndexFlatCodes

in void hnsw_add_vertices() { .... std::unique_ptr dis(storage_distance_computer(index_hnsw.storage)); .... } but i think that DistanceComputer doesnt work for PQ

Which method is actually used by HNSWPQ? For these functions,(add, storage_distance_computer, set_query, add_with_locks) i want to know how faiss combined HNSW and PQ in code, but i am confused