| import torch |
| from torch.autograd import Variable |
| from torch.nn.parameter import Parameter |
| |
| from .module import Module |
| from .. import functional as F |
| |
| |
| 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 zeros whenever it encounters the index. |
| max_norm (float, optional): If given, will renormalize the embeddings to always have a norm lesser than this |
| norm_type (float, optional): The p of the p-norm to compute for the max_norm option |
| scale_grad_by_freq (boolean, optional): if given, this will scale gradients by the frequency of |
| the words in the mini-batch. |
| sparse (boolean, optional): if ``True``, gradient w.r.t. 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) |
| |
| Shape: |
| - Input: LongTensor `(N, W)`, N = mini-batch, W = number of indices to extract per mini-batch |
| - Output: `(N, W, embedding_dim)` |
| |
| Notes: |
| Keep in mind that only a limited number of optimizers support |
| sparse gradients: currently it's `optim.SGD` (`cuda` and `cpu`), |
| and `optim.Adagrad` (`cpu`) |
| |
| 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 = Variable(torch.LongTensor([[1,2,4,5],[4,3,2,9]])) |
| >>> embedding(input) |
| |
| Variable containing: |
| (0 ,.,.) = |
| -1.0822 1.2522 0.2434 |
| 0.8393 -0.6062 -0.3348 |
| 0.6597 0.0350 0.0837 |
| 0.5521 0.9447 0.0498 |
| |
| (1 ,.,.) = |
| 0.6597 0.0350 0.0837 |
| -0.1527 0.0877 0.4260 |
| 0.8393 -0.6062 -0.3348 |
| -0.8738 -0.9054 0.4281 |
| [torch.FloatTensor of size 2x4x3] |
| |
| >>> # example with padding_idx |
| >>> embedding = nn.Embedding(10, 3, padding_idx=0) |
| >>> input = Variable(torch.LongTensor([[0,2,0,5]])) |
| >>> embedding(input) |
| |
| Variable containing: |
| (0 ,.,.) = |
| 0.0000 0.0000 0.0000 |
| 0.3452 0.4937 -0.9361 |
| 0.0000 0.0000 0.0000 |
| 0.0706 -2.1962 -0.6276 |
| [torch.FloatTensor of size 1x4x3] |
| |
| """ |
| |
| def __init__(self, num_embeddings, embedding_dim, padding_idx=None, |
| max_norm=None, norm_type=2, scale_grad_by_freq=False, |
| sparse=False): |
| 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 |
| self.weight = Parameter(torch.Tensor(num_embeddings, embedding_dim)) |
| self.sparse = sparse |
| |
| self.reset_parameters() |
| |
| def reset_parameters(self): |
| self.weight.data.normal_(0, 1) |
| if self.padding_idx is not None: |
| self.weight.data[self.padding_idx].fill_(0) |
| |
| def forward(self, input): |
| return F.embedding( |
| input, self.weight, self.padding_idx, self.max_norm, |
| self.norm_type, self.scale_grad_by_freq, self.sparse) |
| |
| def __repr__(self): |
| s = '{name}({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' |
| s += ')' |
| return s.format(name=self.__class__.__name__, **self.__dict__) |
| |
| |
| class EmbeddingBag(Module): |
| r"""Computes sums or means of 'bags' of embeddings, without instantiating the |
| intermediate embeddings. |
| |
| For bags of constant length, |
| * nn.EmbeddingBag with `mode=sum` is equivalent to nn.Embedding followed by `torch.sum(dim=1)` |
| * with `mode=mean` is equivalent to nn.Embedding followed by `torch.mean(dim=1)` |
| |
| However, nn.EmbeddingBag is much more time and memory efficient than using a chain of these |
| operations. |
| |
| 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, will renormalize the embeddings to always have a norm lesser than this |
| norm_type (float, optional): The p of the p-norm to compute for the max_norm option |
| scale_grad_by_freq (boolean, optional): if given, this will scale gradients by the frequency of |
| the words in the dictionary. |
| mode (string, optional): 'sum' | 'mean'. Specifies the way to reduce the bag. Default: 'mean' |
| |
| Attributes: |
| weight (Tensor): the learnable weights of the module of shape (num_embeddings, embedding_dim) |
| |
| Inputs: input, offsets |
| - **input** (N or BxN): LongTensor containing the indices of the embeddings |
| to extract. When `input` is 1D Tensor of shape `N`, |
| an `offsets` Tensor is given, that contains the |
| starting position of each new sequence in the |
| mini-batch. |
| - **offsets** (B or None): LongTensor containing the starting positions of |
| each sample in a mini-batch of variable length |
| sequences. If `input` is 2D (BxN), then offsets |
| does not need to be given, as the `input` is |
| treated as a mini-batch of fixed length sequences |
| of length `N` each. |
| |
| |
| Shape: |
| - Input: LongTensor `N`, N = number of embeddings to extract |
| (or) LongTensor `BxN`, B = number of sequences in mini-batch, |
| N = number of embeddings per sequence |
| - Offsets: LongTensor `B`, B = number of bags. The values are the |
| offsets in `input` for each bag, i.e. the cumsum of lengths. |
| Offsets is not given if Input is 2D `BxN` Tensor, |
| the input is considered to be of fixed-length sequences |
| - Output: `(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 = Variable(torch.LongTensor([1,2,4,5,4,3,2,9])) |
| >>> offsets = Variable(torch.LongTensor([0,4])) |
| >>> embedding_sum(input, offsets) |
| |
| Variable containing: |
| -0.7296 -4.6926 0.3295 |
| -0.5186 -0.5631 -0.2792 |
| [torch.FloatTensor of size 2x3] |
| |
| """ |
| |
| def __init__(self, num_embeddings, embedding_dim, |
| max_norm=None, norm_type=2, scale_grad_by_freq=False, |
| mode='mean'): |
| 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 |
| self.weight = Parameter(torch.Tensor(num_embeddings, embedding_dim)) |
| self.mode = mode |
| |
| self.reset_parameters() |
| |
| def reset_parameters(self): |
| self.weight.data.normal_(0, 1) |
| |
| def forward(self, input, offsets=None): |
| return F.embedding_bag(self.weight, input, offsets, |
| self.max_norm, self.norm_type, |
| self.scale_grad_by_freq, self.mode) |
| |
| def __repr__(self): |
| s = '{name}({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}' |
| s += ')' |
| return s.format(name=self.__class__.__name__, **self.__dict__) |
| |
| # TODO: SparseLinear |
