214 lines
7.4 KiB
C++
214 lines
7.4 KiB
C++
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD+Patents license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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// -*- c++ -*-
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#ifndef FAISS_INDEX_BINARY_IVF_H
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#define FAISS_INDEX_BINARY_IVF_H
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#include <vector>
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#include "IndexBinary.h"
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#include "IndexIVF.h"
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#include "Clustering.h"
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#include "Heap.h"
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namespace faiss {
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struct BinaryInvertedListScanner;
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/** Index based on a inverted file (IVF)
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*
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* In the inverted file, the quantizer (an IndexBinary instance) provides a
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* quantization index for each vector to be added. The quantization
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* index maps to a list (aka inverted list or posting list), where the
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* id of the vector is stored.
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*
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* Otherwise the object is similar to the IndexIVF
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*/
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struct IndexBinaryIVF : IndexBinary {
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/// Acess to the actual data
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InvertedLists *invlists;
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bool own_invlists;
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size_t nprobe; ///< number of probes at query time
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size_t max_codes; ///< max nb of codes to visit to do a query
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/** Select between using a heap or counting to select the k smallest values
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* when scanning inverted lists.
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*/
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bool use_heap = true;
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/// map for direct access to the elements. Enables reconstruct().
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bool maintain_direct_map;
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std::vector<long> direct_map;
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IndexBinary *quantizer; ///< quantizer that maps vectors to inverted lists
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size_t nlist; ///< number of possible key values
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bool own_fields; ///< whether object owns the quantizer
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ClusteringParameters cp; ///< to override default clustering params
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Index *clustering_index; ///< to override index used during clustering
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/** The Inverted file takes a quantizer (an IndexBinary) on input,
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* which implements the function mapping a vector to a list
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* identifier. The pointer is borrowed: the quantizer should not
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* be deleted while the IndexBinaryIVF is in use.
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*/
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IndexBinaryIVF(IndexBinary *quantizer, size_t d, size_t nlist);
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IndexBinaryIVF();
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~IndexBinaryIVF() override;
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void reset() override;
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/// Trains the quantizer
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void train(idx_t n, const uint8_t *x) override;
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void add(idx_t n, const uint8_t *x) override;
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void add_with_ids(idx_t n, const uint8_t *x, const long *xids) override;
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/// same as add_with_ids, with precomputed coarse quantizer
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void add_core (idx_t n, const uint8_t * x, const long *xids,
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const long *precomputed_idx);
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/** Search a set of vectors, that are pre-quantized by the IVF
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* quantizer. Fill in the corresponding heaps with the query
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* results. search() calls this.
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*
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* @param n nb of vectors to query
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* @param x query vectors, size nx * d
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* @param assign coarse quantization indices, size nx * nprobe
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* @param centroid_dis
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* distances to coarse centroids, size nx * nprobe
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* @param distance
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* output distances, size n * k
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* @param labels output labels, size n * k
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* @param store_pairs store inv list index + inv list offset
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* instead in upper/lower 32 bit of result,
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* instead of ids (used for reranking).
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* @param params used to override the object's search parameters
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*/
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void search_preassigned(idx_t n, const uint8_t *x, idx_t k,
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const idx_t *assign,
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const int32_t *centroid_dis,
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int32_t *distances, idx_t *labels,
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bool store_pairs,
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const IVFSearchParameters *params=nullptr
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) const;
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virtual BinaryInvertedListScanner *get_InvertedListScanner (
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bool store_pairs=false) const;
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/** assign the vectors, then call search_preassign */
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virtual void search(idx_t n, const uint8_t *x, idx_t k,
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int32_t *distances, idx_t *labels) const override;
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void reconstruct(idx_t key, uint8_t *recons) const override;
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/** Reconstruct a subset of the indexed vectors.
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*
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* Overrides default implementation to bypass reconstruct() which requires
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* direct_map to be maintained.
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*
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* @param i0 first vector to reconstruct
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* @param ni nb of vectors to reconstruct
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* @param recons output array of reconstructed vectors, size ni * d / 8
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*/
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void reconstruct_n(idx_t i0, idx_t ni, uint8_t *recons) const override;
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/** Similar to search, but also reconstructs the stored vectors (or an
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* approximation in the case of lossy coding) for the search results.
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*
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* Overrides default implementation to avoid having to maintain direct_map
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* and instead fetch the code offsets through the `store_pairs` flag in
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* search_preassigned().
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*
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* @param recons reconstructed vectors size (n, k, d / 8)
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*/
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void search_and_reconstruct(idx_t n, const uint8_t *x, idx_t k,
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int32_t *distances, idx_t *labels,
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uint8_t *recons) const override;
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/** Reconstruct a vector given the location in terms of (inv list index +
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* inv list offset) instead of the id.
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*
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* Useful for reconstructing when the direct_map is not maintained and
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* the inv list offset is computed by search_preassigned() with
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* `store_pairs` set.
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*/
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virtual void reconstruct_from_offset(long list_no, long offset,
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uint8_t* recons) const;
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/// Dataset manipulation functions
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long remove_ids(const IDSelector& sel) override;
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/** moves the entries from another dataset to self. On output,
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* other is empty. add_id is added to all moved ids (for
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* sequential ids, this would be this->ntotal */
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virtual void merge_from(IndexBinaryIVF& other, idx_t add_id);
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size_t get_list_size(size_t list_no) const
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{ return invlists->list_size(list_no); }
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/** intialize a direct map
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*
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* @param new_maintain_direct_map if true, create a direct map,
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* else clear it
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*/
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void make_direct_map(bool new_maintain_direct_map=true);
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void replace_invlists(InvertedLists *il, bool own=false);
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};
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struct BinaryInvertedListScanner {
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using idx_t = Index::idx_t;
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/// from now on we handle this query.
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virtual void set_query (const uint8_t *query_vector) = 0;
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/// following codes come from this inverted list
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virtual void set_list (idx_t list_no, uint8_t coarse_dis) = 0;
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/// compute a single query-to-code distance
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virtual uint32_t distance_to_code (const uint8_t *code) const = 0;
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/** compute the distances to codes. (distances, labels) should be
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* organized as a min- or max-heap
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*
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* @param n number of codes to scan
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* @param codes codes to scan (n * code_size)
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* @param ids corresponding ids (ignored if store_pairs)
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* @param distances heap distances (size k)
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* @param labels heap labels (size k)
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* @param k heap size
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*/
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virtual size_t scan_codes (size_t n,
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const uint8_t *codes,
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const idx_t *ids,
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int32_t *distances, idx_t *labels,
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size_t k) const = 0;
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virtual ~BinaryInvertedListScanner () {}
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};
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} // namespace faiss
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#endif // FAISS_INDEX_BINARY_IVF_H
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