from typing import Optional
import torch
from torch import Tensor
from torch.nn.parameter import Parameter
from .module import Module
from .. import functional as F
from .. import init
[docs]class Embedding(Module):
r"""A simple lookup table that stores embeddings of a fixed dictionary and size.
This module is often used to store word embeddings and retrieve them using indices.
The input to the module is a list of indices, and the output is the corresponding
word embeddings.
Args:
num_embeddings (int): size of the dictionary of embeddings
embedding_dim (int): the size of each embedding vector
padding_idx (int, optional): If given, pads the output with the embedding vector at :attr:`padding_idx`
(initialized to zeros) whenever it encounters the index.
max_norm (float, optional): If given, each embedding vector with norm larger than :attr:`max_norm`
is renormalized to have norm :attr:`max_norm`.
norm_type (float, optional): The p of the p-norm to compute for the :attr:`max_norm` option. Default ``2``.
scale_grad_by_freq (boolean, optional): If given, this will scale gradients by the inverse of frequency of
the words in the mini-batch. Default ``False``.
sparse (bool, optional): If ``True``, gradient w.r.t. :attr:`weight` matrix will be a sparse tensor.
See Notes for more details regarding sparse gradients.
Attributes:
weight (Tensor): the learnable weights of the module of shape (num_embeddings, embedding_dim)
initialized from :math:`\mathcal{N}(0, 1)`
Shape:
- Input: :math:`(*)`, LongTensor of arbitrary shape containing the indices to extract
- Output: :math:`(*, H)`, where `*` is the input shape and :math:`H=\text{embedding\_dim}`
.. note::
Keep in mind that only a limited number of optimizers support
sparse gradients: currently it's :class:`optim.SGD` (`CUDA` and `CPU`),
:class:`optim.SparseAdam` (`CUDA` and `CPU`) and :class:`optim.Adagrad` (`CPU`)
.. note::
With :attr:`padding_idx` set, the embedding vector at
:attr:`padding_idx` is initialized to all zeros. However, note that this
vector can be modified afterwards, e.g., using a customized
initialization method, and thus changing the vector used to pad the
output. The gradient for this vector from :class:`~torch.nn.Embedding`
is always zero.
Examples::
>>> # an Embedding module containing 10 tensors of size 3
>>> embedding = nn.Embedding(10, 3)
>>> # a batch of 2 samples of 4 indices each
>>> input = torch.LongTensor([[1,2,4,5],[4,3,2,9]])
>>> embedding(input)
tensor([[[-0.0251, -1.6902, 0.7172],
[-0.6431, 0.0748, 0.6969],
[ 1.4970, 1.3448, -0.9685],
[-0.3677, -2.7265, -0.1685]],
[[ 1.4970, 1.3448, -0.9685],
[ 0.4362, -0.4004, 0.9400],
[-0.6431, 0.0748, 0.6969],
[ 0.9124, -2.3616, 1.1151]]])
>>> # example with padding_idx
>>> embedding = nn.Embedding(10, 3, padding_idx=0)
>>> input = torch.LongTensor([[0,2,0,5]])
>>> embedding(input)
tensor([[[ 0.0000, 0.0000, 0.0000],
[ 0.1535, -2.0309, 0.9315],
[ 0.0000, 0.0000, 0.0000],
[-0.1655, 0.9897, 0.0635]]])
"""
__constants__ = ['num_embeddings', 'embedding_dim', 'padding_idx', 'max_norm',
'norm_type', 'scale_grad_by_freq', 'sparse']
num_embeddings: int
embedding_dim: int
padding_idx: int
max_norm: float
norm_type: float
scale_grad_by_freq: bool
weight: Tensor
sparse: bool
def __init__(self, num_embeddings: int, embedding_dim: int, padding_idx: Optional[int] = None,
max_norm: Optional[float] = None, norm_type: float = 2., scale_grad_by_freq: bool = False,
sparse: bool = False, _weight: Optional[Tensor] = None) -> None:
super(Embedding, self).__init__()
self.num_embeddings = num_embeddings
self.embedding_dim = embedding_dim
if padding_idx is not None:
if padding_idx > 0:
assert padding_idx < self.num_embeddings, 'Padding_idx must be within num_embeddings'
elif padding_idx < 0:
assert padding_idx >= -self.num_embeddings, 'Padding_idx must be within num_embeddings'
padding_idx = self.num_embeddings + padding_idx
self.padding_idx = padding_idx
self.max_norm = max_norm
self.norm_type = norm_type
self.scale_grad_by_freq = scale_grad_by_freq
if _weight is None:
self.weight = Parameter(torch.Tensor(num_embeddings, embedding_dim))
self.reset_parameters()
else:
assert list(_weight.shape) == [num_embeddings, embedding_dim], \
'Shape of weight does not match num_embeddings and embedding_dim'
self.weight = Parameter(_weight)
self.sparse = sparse
def reset_parameters(self) -> None:
init.normal_(self.weight)
if self.padding_idx is not None:
with torch.no_grad():
self.weight[self.padding_idx].fill_(0)
def forward(self, input: Tensor) -> Tensor:
return F.embedding(
input, self.weight, self.padding_idx, self.max_norm,
self.norm_type, self.scale_grad_by_freq, self.sparse)
def extra_repr(self) -> str:
s = '{num_embeddings}, {embedding_dim}'
if self.padding_idx is not None:
s += ', padding_idx={padding_idx}'
if self.max_norm is not None:
s += ', max_norm={max_norm}'
if self.norm_type != 2:
s += ', norm_type={norm_type}'
if self.scale_grad_by_freq is not False:
s += ', scale_grad_by_freq={scale_grad_by_freq}'
if self.sparse is not False:
s += ', sparse=True'
return s.format(**self.__dict__)
[docs] @classmethod
def from_pretrained(cls, embeddings, freeze=True, padding_idx=None,
max_norm=None, norm_type=2., scale_grad_by_freq=False,
sparse=False):
r"""Creates Embedding instance from given 2-dimensional FloatTensor.
Args:
embeddings (Tensor): FloatTensor containing weights for the Embedding.
First dimension is being passed to Embedding as ``num_embeddings``, second as ``embedding_dim``.
freeze (boolean, optional): If ``True``, the tensor does not get updated in the learning process.
Equivalent to ``embedding.weight.requires_grad = False``. Default: ``True``
padding_idx (int, optional): See module initialization documentation.
max_norm (float, optional): See module initialization documentation.
norm_type (float, optional): See module initialization documentation. Default ``2``.
scale_grad_by_freq (boolean, optional): See module initialization documentation. Default ``False``.
sparse (bool, optional): See module initialization documentation.
Examples::
>>> # FloatTensor containing pretrained weights
>>> weight = torch.FloatTensor([[1, 2.3, 3], [4, 5.1, 6.3]])
>>> embedding = nn.Embedding.from_pretrained(weight)
>>> # Get embeddings for index 1
>>> input = torch.LongTensor([1])
>>> embedding(input)
tensor([[ 4.0000, 5.1000, 6.3000]])
"""
assert embeddings.dim() == 2, \
'Embeddings parameter is expected to be 2-dimensional'
rows, cols = embeddings.shape
embedding = cls(
num_embeddings=rows,
embedding_dim=cols,
_weight=embeddings,
padding_idx=padding_idx,
max_norm=max_norm,
norm_type=norm_type,
scale_grad_by_freq=scale_grad_by_freq,
sparse=sparse)
embedding.weight.requires_grad = not freeze
return embedding
[docs]class EmbeddingBag(Module):
r"""Computes sums or means of 'bags' of embeddings, without instantiating the
intermediate embeddings.
For bags of constant length and no :attr:`per_sample_weights`, this class
* with ``mode="sum"`` is equivalent to :class:`~torch.nn.Embedding` followed by ``torch.sum(dim=0)``,
* with ``mode="mean"`` is equivalent to :class:`~torch.nn.Embedding` followed by ``torch.mean(dim=0)``,
* with ``mode="max"`` is equivalent to :class:`~torch.nn.Embedding` followed by ``torch.max(dim=0)``.
However, :class:`~torch.nn.EmbeddingBag` is much more time and memory efficient than using a chain of these
operations.
EmbeddingBag also supports per-sample weights as an argument to the forward
pass. This scales the output of the Embedding before performing a weighted
reduction as specified by ``mode``. If :attr:`per_sample_weights`` is passed, the
only supported ``mode`` is ``"sum"``, which computes a weighted sum according to
:attr:`per_sample_weights`.
Args:
num_embeddings (int): size of the dictionary of embeddings
embedding_dim (int): the size of each embedding vector
max_norm (float, optional): If given, each embedding vector with norm larger than :attr:`max_norm`
is renormalized to have norm :attr:`max_norm`.
norm_type (float, optional): The p of the p-norm to compute for the :attr:`max_norm` option. Default ``2``.
scale_grad_by_freq (boolean, optional): if given, this will scale gradients by the inverse of frequency of
the words in the mini-batch. Default ``False``.
Note: this option is not supported when ``mode="max"``.
mode (string, optional): ``"sum"``, ``"mean"`` or ``"max"``. Specifies the way to reduce the bag.
``"sum"`` computes the weighted sum, taking :attr:`per_sample_weights`
into consideration. ``"mean"`` computes the average of the values
in the bag, ``"max"`` computes the max value over each bag.
Default: ``"mean"``
sparse (bool, optional): if ``True``, gradient w.r.t. :attr:`weight` matrix will be a sparse tensor. See
Notes for more details regarding sparse gradients. Note: this option is not
supported when ``mode="max"``.
include_last_offset (bool, optional): if ``True``, :attr:`offsets` has one additional element, where the last element
is equivalent to the size of `indices`. This matches the CSR format. Note:
this option is currently only supported when ``mode="sum"``.
Attributes:
weight (Tensor): the learnable weights of the module of shape `(num_embeddings, embedding_dim)`
initialized from :math:`\mathcal{N}(0, 1)`.
Inputs: :attr:`input` (LongTensor), :attr:`offsets` (LongTensor, optional), and
:attr:`per_index_weights` (Tensor, optional)
- If :attr:`input` is 2D of shape `(B, N)`,
it will be treated as ``B`` bags (sequences) each of fixed length ``N``, and
this will return ``B`` values aggregated in a way depending on the :attr:`mode`.
:attr:`offsets` is ignored and required to be ``None`` in this case.
- If :attr:`input` is 1D of shape `(N)`,
it will be treated as a concatenation of multiple bags (sequences).
:attr:`offsets` is required to be a 1D tensor containing the
starting index positions of each bag in :attr:`input`. Therefore,
for :attr:`offsets` of shape `(B)`, :attr:`input` will be viewed as
having ``B`` bags. Empty bags (i.e., having 0-length) will have
returned vectors filled by zeros.
per_sample_weights (Tensor, optional): a tensor of float / double weights, or None
to indicate all weights should be taken to be ``1``. If specified, :attr:`per_sample_weights`
must have exactly the same shape as input and is treated as having the same
:attr:`offsets`, if those are not ``None``. Only supported for ``mode='sum'``.
Output shape: `(B, embedding_dim)`
Examples::
>>> # an Embedding module containing 10 tensors of size 3
>>> embedding_sum = nn.EmbeddingBag(10, 3, mode='sum')
>>> # a batch of 2 samples of 4 indices each
>>> input = torch.LongTensor([1,2,4,5,4,3,2,9])
>>> offsets = torch.LongTensor([0,4])
>>> embedding_sum(input, offsets)
tensor([[-0.8861, -5.4350, -0.0523],
[ 1.1306, -2.5798, -1.0044]])
"""
__constants__ = ['num_embeddings', 'embedding_dim', 'max_norm', 'norm_type',
'scale_grad_by_freq', 'mode', 'sparse', 'include_last_offset']
num_embeddings: int
embedding_dim: int
max_norm: float
norm_type: float
scale_grad_by_freq: bool
weight: Tensor
mode: str
sparse: bool
include_last_offset: bool
def __init__(self, num_embeddings: int, embedding_dim: int,
max_norm: Optional[float] = None, norm_type: float = 2., scale_grad_by_freq: bool = False,
mode: str = 'mean', sparse: bool = False, _weight: Optional[Tensor] = None,
include_last_offset: bool = False) -> None:
super(EmbeddingBag, self).__init__()
self.num_embeddings = num_embeddings
self.embedding_dim = embedding_dim
self.max_norm = max_norm
self.norm_type = norm_type
self.scale_grad_by_freq = scale_grad_by_freq
if _weight is None:
self.weight = Parameter(torch.Tensor(num_embeddings, embedding_dim))
self.reset_parameters()
else:
assert list(_weight.shape) == [num_embeddings, embedding_dim], \
'Shape of weight does not match num_embeddings and embedding_dim'
self.weight = Parameter(_weight)
self.mode = mode
self.sparse = sparse
self.include_last_offset = include_last_offset
def reset_parameters(self) -> None:
init.normal_(self.weight)
def forward(self, input: Tensor, offsets: Optional[Tensor] = None, per_sample_weights: Optional[Tensor] = None) -> Tensor:
return F.embedding_bag(input, self.weight, offsets,
self.max_norm, self.norm_type,
self.scale_grad_by_freq, self.mode, self.sparse,
per_sample_weights, self.include_last_offset)
def extra_repr(self) -> str:
s = '{num_embeddings}, {embedding_dim}'
if self.max_norm is not None:
s += ', max_norm={max_norm}'
if self.norm_type != 2:
s += ', norm_type={norm_type}'
if self.scale_grad_by_freq is not False:
s += ', scale_grad_by_freq={scale_grad_by_freq}'
s += ', mode={mode}'
return s.format(**self.__dict__)
[docs] @classmethod
def from_pretrained(cls, embeddings: Tensor, freeze: bool = True, max_norm: Optional[float] = None,
norm_type: float = 2., scale_grad_by_freq: bool = False,
mode: str = 'mean', sparse: bool = False, include_last_offset: bool = False) -> 'EmbeddingBag':
r"""Creates EmbeddingBag instance from given 2-dimensional FloatTensor.
Args:
embeddings (Tensor): FloatTensor containing weights for the EmbeddingBag.
First dimension is being passed to EmbeddingBag as 'num_embeddings', second as 'embedding_dim'.
freeze (boolean, optional): If ``True``, the tensor does not get updated in the learning process.
Equivalent to ``embeddingbag.weight.requires_grad = False``. Default: ``True``
max_norm (float, optional): See module initialization documentation. Default: ``None``
norm_type (float, optional): See module initialization documentation. Default ``2``.
scale_grad_by_freq (boolean, optional): See module initialization documentation. Default ``False``.
mode (string, optional): See module initialization documentation. Default: ``"mean"``
sparse (bool, optional): See module initialization documentation. Default: ``False``.
include_last_offset (bool, optional): See module initialization documentation. Default: ``False``.
Examples::
>>> # FloatTensor containing pretrained weights
>>> weight = torch.FloatTensor([[1, 2.3, 3], [4, 5.1, 6.3]])
>>> embeddingbag = nn.EmbeddingBag.from_pretrained(weight)
>>> # Get embeddings for index 1
>>> input = torch.LongTensor([[1, 0]])
>>> embeddingbag(input)
tensor([[ 2.5000, 3.7000, 4.6500]])
"""
assert embeddings.dim() == 2, \
'Embeddings parameter is expected to be 2-dimensional'
rows, cols = embeddings.shape
embeddingbag = cls(
num_embeddings=rows,
embedding_dim=cols,
_weight=embeddings,
max_norm=max_norm,
norm_type=norm_type,
scale_grad_by_freq=scale_grad_by_freq,
mode=mode,
sparse=sparse,
include_last_offset=include_last_offset)
embeddingbag.weight.requires_grad = not freeze
return embeddingbag
