spaCy/spacy/ml/_legacy_tok2vec.py
Matthew Honnibal 3e78e82a83
Experimental character-based pretraining (#5700)
* Use cosine loss in Cloze multitask

* Fix char_embed for gpu

* Call resume_training for base model in train CLI

* Fix bilstm_depth default in pretrain command

* Implement character-based pretraining objective

* Use chars loss in ClozeMultitask

* Add method to decode predicted characters

* Fix number characters

* Rescale gradients for mlm

* Fix char embed+vectors in ml

* Fix pipes

* Fix pretrain args

* Move get_characters_loss

* Fix import

* Fix import

* Mention characters loss option in pretrain

* Remove broken 'self attention' option in pretrain

* Revert "Remove broken 'self attention' option in pretrain"

This reverts commit 56b820f6af.

* Document 'characters' objective of pretrain
2020-07-05 15:48:39 +02:00

141 lines
5.0 KiB
Python

# coding: utf8
from __future__ import unicode_literals
from thinc.v2v import Model, Maxout
from thinc.i2v import HashEmbed, StaticVectors
from thinc.t2t import ExtractWindow
from thinc.misc import Residual
from thinc.misc import LayerNorm as LN
from thinc.misc import FeatureExtracter
from thinc.api import layerize, chain, clone, concatenate, with_flatten
from thinc.api import uniqued, wrap, noop
from ..attrs import ID, ORTH, NORM, PREFIX, SUFFIX, SHAPE
def Tok2Vec(width, embed_size, **kwargs):
# Circular imports :(
from .._ml import CharacterEmbed
from .._ml import PyTorchBiLSTM
pretrained_vectors = kwargs.get("pretrained_vectors", None)
cnn_maxout_pieces = kwargs.get("cnn_maxout_pieces", 3)
subword_features = kwargs.get("subword_features", True)
char_embed = kwargs.get("char_embed", False)
if char_embed:
subword_features = False
conv_depth = kwargs.get("conv_depth", 4)
bilstm_depth = kwargs.get("bilstm_depth", 0)
cols = [ID, NORM, PREFIX, SUFFIX, SHAPE, ORTH]
with Model.define_operators({">>": chain, "|": concatenate, "**": clone}):
norm = HashEmbed(width, embed_size, column=cols.index(NORM), name="embed_norm")
if subword_features:
prefix = HashEmbed(
width, embed_size // 2, column=cols.index(PREFIX), name="embed_prefix"
)
suffix = HashEmbed(
width, embed_size // 2, column=cols.index(SUFFIX), name="embed_suffix"
)
shape = HashEmbed(
width, embed_size // 2, column=cols.index(SHAPE), name="embed_shape"
)
else:
prefix, suffix, shape = (None, None, None)
if pretrained_vectors is not None:
glove = StaticVectors(pretrained_vectors, width, column=cols.index(ID))
if subword_features:
embed = uniqued(
(glove | norm | prefix | suffix | shape)
>> LN(Maxout(width, width * 5, pieces=3)),
column=cols.index(ORTH),
)
elif char_embed:
embed = concatenate_lists(
CharacterEmbed(nM=64, nC=8),
FeatureExtracter(cols) >> with_flatten(glove),
)
reduce_dimensions = LN(
Maxout(width, 64 * 8 + width, pieces=cnn_maxout_pieces)
)
else:
embed = uniqued(
(glove | norm) >> LN(Maxout(width, width * 2, pieces=3)),
column=cols.index(ORTH),
)
elif subword_features:
embed = uniqued(
(norm | prefix | suffix | shape)
>> LN(Maxout(width, width * 4, pieces=3)),
column=cols.index(ORTH),
)
elif char_embed:
embed = concatenate_lists(
CharacterEmbed(nM=64, nC=8),
FeatureExtracter(cols) >> with_flatten(norm),
)
reduce_dimensions = LN(
Maxout(width, 64 * 8 + width, pieces=cnn_maxout_pieces)
)
else:
embed = norm
convolution = Residual(
ExtractWindow(nW=1)
>> LN(Maxout(width, width * 3, pieces=cnn_maxout_pieces))
)
if char_embed:
tok2vec = embed >> with_flatten(
reduce_dimensions >> convolution ** conv_depth, pad=conv_depth
)
else:
tok2vec = FeatureExtracter(cols) >> with_flatten(
embed
>> convolution ** conv_depth, pad=conv_depth
)
if bilstm_depth >= 1:
tok2vec = tok2vec >> PyTorchBiLSTM(width, width, bilstm_depth)
# Work around thinc API limitations :(. TODO: Revise in Thinc 7
tok2vec.nO = width
tok2vec.embed = embed
return tok2vec
@layerize
def flatten(seqs, drop=0.0):
ops = Model.ops
lengths = ops.asarray([len(seq) for seq in seqs], dtype="i")
def finish_update(d_X, sgd=None):
return ops.unflatten(d_X, lengths, pad=0)
X = ops.flatten(seqs, pad=0)
return X, finish_update
def concatenate_lists(*layers, **kwargs): # pragma: no cover
"""Compose two or more models `f`, `g`, etc, such that their outputs are
concatenated, i.e. `concatenate(f, g)(x)` computes `hstack(f(x), g(x))`
"""
if not layers:
return noop()
drop_factor = kwargs.get("drop_factor", 1.0)
ops = layers[0].ops
layers = [chain(layer, flatten) for layer in layers]
concat = concatenate(*layers)
def concatenate_lists_fwd(Xs, drop=0.0):
if drop is not None:
drop *= drop_factor
lengths = ops.asarray([len(X) for X in Xs], dtype="i")
flat_y, bp_flat_y = concat.begin_update(Xs, drop=drop)
ys = ops.unflatten(flat_y, lengths)
def concatenate_lists_bwd(d_ys, sgd=None):
return bp_flat_y(ops.flatten(d_ys), sgd=sgd)
return ys, concatenate_lists_bwd
model = wrap(concatenate_lists_fwd, concat)
return model