spaCy/spacy/kb.pxd

152 lines
6.0 KiB
Cython

"""Knowledge-base for entity or concept linking."""
from cymem.cymem cimport Pool
from preshed.maps cimport PreshMap
from libcpp.vector cimport vector
from libc.stdint cimport int32_t, int64_t
from spacy.strings cimport StringStore
from .typedefs cimport hash_t
# Internal struct, for storage and disambiguation. This isn't what we return
# to the user as the answer to "here's your entity". It's the minimum number
# of bits we need to keep track of the answers.
cdef struct _EntryC:
# The hash of this entry's unique ID and name in the kB
hash_t entity_id_hash
hash_t entity_name_hash
# Allows retrieval of one or more vectors.
# Each element of vector_rows should be an index into a vectors table.
# Every entry should have the same number of vectors, so we can avoid storing
# the number of vectors in each knowledge-base struct
int32_t* vector_rows
# Allows retrieval of a struct of non-vector features. We could make this a
# pointer, but we have 32 bits left over in the struct after prob, so we'd
# like this to only be 32 bits. We can also set this to -1, for the common
# case where there are no features.
int32_t feats_row
# log probability of entity, based on corpus frequency
float prob
# Each alias struct stores a list of Entry pointers with their prior probabilities
# for this specific mention/alias.
cdef struct _AliasC:
# All entry candidates for this alias
vector[int64_t] entry_indices
# Prior probability P(entity|alias) - should sum up to (at most) 1.
vector[float] probs
# Object used by the Entity Linker that summarizes one entity-alias candidate combination.
cdef class Candidate:
cdef readonly KnowledgeBase kb
cdef hash_t entity_id_hash
cdef hash_t alias_hash
cdef float prior_prob
cdef class KnowledgeBase:
cdef Pool mem
cpdef readonly StringStore strings
# This maps 64bit keys (hash of unique entity string)
# to 64bit values (position of the _EntryC struct in the _entries vector).
# The PreshMap is pretty space efficient, as it uses open addressing. So
# the only overhead is the vacancy rate, which is approximately 30%.
cdef PreshMap _entry_index
# Each entry takes 128 bits, and again we'll have a 30% or so overhead for
# over allocation.
# In total we end up with (N*128*1.3)+(N*128*1.3) bits for N entries.
# Storing 1m entries would take 41.6mb under this scheme.
cdef vector[_EntryC] _entries
# This maps 64bit keys (hash of unique alias string)
# to 64bit values (position of the _AliasC struct in the _aliases_table vector).
cdef PreshMap _alias_index
# This should map mention hashes to (entry_id, prob) tuples. The probability
# should be P(entity | mention), which is pretty important to know.
# We can pack both pieces of information into a 64-bit value, to keep things
# efficient.
cdef vector[_AliasC] _aliases_table
# This is the part which might take more space: storing various
# categorical features for the entries, and storing vectors for disambiguation
# and possibly usage.
# If each entry gets a 300-dimensional vector, for 1m entries we would need
# 1.2gb. That gets expensive fast. What might be better is to avoid learning
# a unique vector for every entity. We could instead have a compositional
# model, that embeds different features of the entities into vectors. We'll
# still want some per-entity features, like the Wikipedia text or entity
# co-occurrence. Hopefully those vectors can be narrow, e.g. 64 dimensions.
cdef object _vectors_table
# It's very useful to track categorical features, at least for output, even
# if they're not useful in the model itself. For instance, we should be
# able to track stuff like a person's date of birth or whatever. This can
# easily make the KB bigger, but if this isn't needed by the model, and it's
# optional data, we can let users configure a DB as the backend for this.
cdef object _features_table
cdef inline int64_t c_add_entity(self, hash_t entity_id_hash, hash_t entity_name_hash, float prob,
int32_t* vector_rows, int feats_row):
"""Add an entry to the knowledge base."""
# This is what we'll map the hash key to. It's where the entry will sit
# in the vector of entries, so we can get it later.
cdef int64_t new_index = self._entries.size()
self._entries.push_back(
_EntryC(
entity_id_hash=entity_id_hash,
entity_name_hash=entity_name_hash,
vector_rows=vector_rows,
feats_row=feats_row,
prob=prob
))
self._entry_index[entity_id_hash] = new_index
return new_index
cdef inline int64_t c_add_aliases(self, hash_t alias_hash, vector[int64_t] entry_indices, vector[float] probs):
"""Connect a mention to a list of potential entities with their prior probabilities ."""
cdef int64_t new_index = self._aliases_table.size()
self._aliases_table.push_back(
_AliasC(
entry_indices=entry_indices,
probs=probs
))
self._alias_index[alias_hash] = new_index
return new_index
cdef inline _create_empty_vectors(self):
"""
Making sure the first element of each vector is a dummy,
because the PreshMap maps pointing to indices in these vectors can not contain 0 as value
cf. https://github.com/explosion/preshed/issues/17
"""
cdef int32_t dummy_value = 0
self.strings.add("")
self._entries.push_back(
_EntryC(
entity_id_hash=self.strings[""],
entity_name_hash=self.strings[""],
vector_rows=&dummy_value,
feats_row=dummy_value,
prob=dummy_value
))
self._aliases_table.push_back(
_AliasC(
entry_indices=[dummy_value],
probs=[dummy_value]
))