Struct faiss::OnDiskInvertedLists

struct OnDiskInvertedLists : public faiss::InvertedLists

On-disk storage of inverted lists.

The data is stored in a mmapped chunk of memory (base pointer ptr, size totsize). Each list is a range of memory that contains (object List) that contains:

uint8_t codes[capacity * code_size]
followed by idx_t ids[capacity]

in each of the arrays, the size <= capacity first elements are used, the rest is not initialized.

Addition and resize are supported by:

roundind up the capacity of the lists to a power of two
maintaining a list of empty slots, sorted by size.
resizing the mmapped block is adjusted as needed.

An OnDiskInvertedLists is compact if the size == capacity for all lists and there are no available slots.

Addition to the invlists is slow. For incremental add it is better to use a default ArrayInvertedLists object and convert it to an OnDisk with merge_from.

When it is known that a set of lists will be accessed, it is useful to call prefetch_lists, that launches a set of threads to read the lists in parallel.

Public Types

using List = OnDiskOneList

enum subset_type_t

Values:

enumerator SUBSET_TYPE_ID_RANGE

enumerator SUBSET_TYPE_ID_MOD

enumerator SUBSET_TYPE_ELEMENT_RANGE

enumerator SUBSET_TYPE_INVLIST_FRACTION

enumerator SUBSET_TYPE_INVLIST

Public Functions

OnDiskInvertedLists(size_t nlist, size_t code_size, const char *filename): are inverted lists mapped read-only

virtual size_t list_size(size_t list_no) const override: get the size of a list

virtual const uint8_t *get_codes(size_t list_no) const override

get the codes for an inverted list must be released by release_codes

Returns:: codes size list_size * code_size

virtual const idx_t *get_ids(size_t list_no) const override

get the ids for an inverted list must be released by release_ids

Returns:: ids size list_size

virtual size_t add_entries(size_t list_no, size_t n_entry, const idx_t *ids, const uint8_t *code) override

virtual void update_entries(size_t list_no, size_t offset, size_t n_entry, const idx_t *ids, const uint8_t *code) override

virtual void resize(size_t list_no, size_t new_size) override

size_t merge_from_multiple(const InvertedLists **ils, int n_il, bool shift_ids = false, bool verbose = false)

size_t merge_from_1(const InvertedLists *il, bool verbose = false): same as merge_from for a single invlist

void crop_invlists(size_t l0, size_t l1): restrict the inverted lists to l0:l1 without touching the mmapped region

virtual void prefetch_lists(const idx_t *list_nos, int nlist) const override: prepare the following lists (default does nothing) a list can be -1 hence the signed long

~OnDiskInvertedLists() override

void do_mmap()

void update_totsize(size_t new_totsize)

void resize_locked(size_t list_no, size_t new_size)

size_t allocate_slot(size_t capacity)

void free_slot(size_t offset, size_t capacity)

void set_all_lists_sizes(const size_t *sizes): override all list sizes and make a packed storage

OnDiskInvertedLists()

virtual void release_codes(size_t list_no, const uint8_t *codes) const: release codes returned by get_codes (default implementation is nop

virtual void release_ids(size_t list_no, const idx_t *ids) const: release ids returned by get_ids

virtual idx_t get_single_id(size_t list_no, size_t offset) const

Returns:: a single id in an inverted list

virtual const uint8_t *get_single_code(size_t list_no, size_t offset) const

Returns:: a single code in an inverted list (should be deallocated with release_codes)

virtual bool is_empty(size_t list_no, void *inverted_list_context = nullptr) const: check if the list is empty

virtual InvertedListsIterator *get_iterator(size_t list_no, void *inverted_list_context = nullptr) const: get iterable for lists that use_iterator

virtual size_t add_entry(size_t list_no, idx_t theid, const uint8_t *code, void *inverted_list_context = nullptr): add one entry to an inverted list

virtual void update_entry(size_t list_no, size_t offset, idx_t id, const uint8_t *code)

virtual void reset()

void merge_from(InvertedLists *oivf, size_t add_id): move all entries from oivf (empty on output)

size_t copy_subset_to(InvertedLists &other, subset_type_t subset_type, idx_t a1, idx_t a2) const

copy a subset of the entries index to the other index

Returns:: number of entries copied

double imbalance_factor() const: 1= perfectly balanced, >1: imbalanced

void print_stats() const: display some stats about the inverted lists

size_t compute_ntotal() const: sum up list sizes

Public Members

std::vector<List> lists

std::list<Slot> slots

std::string filename

size_t totsize

uint8_t *ptr

bool read_only

LockLevels *locks

OngoingPrefetch *pf

int prefetch_nthread

size_t nlist: number of possible key values

size_t code_size: code size per vector in bytes

bool use_iterator = false: request to use iterator rather than get_codes / get_ids

Public Static Attributes

static const size_t INVALID_CODE_SIZE = static_cast<size_t>(-1): used for BlockInvertedLists, where the codes are packed into groups and the individual code size is meaningless

struct Slot

Public Functions

Slot(size_t offset, size_t capacity)

Slot()

Public Members

size_t offset

size_t capacity