Source code for transformers.modeling_ctrl

# coding=utf-8
# Copyright 2018 Salesforce and HuggingFace Inc. team.
# Copyright (c) 2018, NVIDIA CORPORATION.  All rights reserved.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.
""" PyTorch CTRL model."""

import warnings

import numpy as np
import torch
import torch.nn as nn
from torch.nn import CrossEntropyLoss

from .configuration_ctrl import CTRLConfig
from .file_utils import add_code_sample_docstrings, add_start_docstrings, add_start_docstrings_to_callable
from .modeling_outputs import BaseModelOutputWithPast, CausalLMOutputWithPast
from .modeling_utils import Conv1D, PreTrainedModel, find_pruneable_heads_and_indices, prune_linear_layer
from .utils import logging

logger = logging.get_logger(__name__)


    # See all CTRL models at

def angle_defn(pos, i, d_model_size):
    angle_rates = 1 / torch.pow(10000, (2 * (i // 2)) / d_model_size)
    return pos * angle_rates

def positional_encoding(position, d_model_size, dtype):
    # create the sinusoidal pattern for the positional encoding
    angle_rads = angle_defn(
        torch.arange(position, dtype=dtype).unsqueeze(1),
        torch.arange(d_model_size, dtype=dtype).unsqueeze(0),

    sines = torch.sin(angle_rads[:, 0::2])
    cosines = torch.cos(angle_rads[:, 1::2])

    pos_encoding =[sines, cosines], dim=-1)
    return pos_encoding

def scaled_dot_product_attention(q, k, v, mask, attention_mask=None, head_mask=None):
    # calculate attention
    matmul_qk = torch.matmul(q, k.permute(0, 1, 3, 2))

    dk = k.shape[-1]
    scaled_attention_logits = matmul_qk / np.sqrt(dk)

    if mask is not None:
        nd, ns = scaled_attention_logits.size(-2), scaled_attention_logits.size(-1)
        scaled_attention_logits += mask[ns - nd : ns, :ns] * -1e4

    if attention_mask is not None:
        # Apply the attention mask
        scaled_attention_logits = scaled_attention_logits + attention_mask

    attention_weights = torch.softmax(scaled_attention_logits, dim=-1)

    # Mask heads if we want to
    if head_mask is not None:
        attention_weights = attention_weights * head_mask

    output = torch.matmul(attention_weights, v)

    return output, attention_weights

class MultiHeadAttention(torch.nn.Module):
    def __init__(self, d_model_size, num_heads):
        self.num_heads = num_heads
        self.d_model_size = d_model_size

        self.depth = int(d_model_size / self.num_heads)

        self.Wq = torch.nn.Linear(d_model_size, d_model_size)
        self.Wk = torch.nn.Linear(d_model_size, d_model_size)
        self.Wv = torch.nn.Linear(d_model_size, d_model_size)

        self.dense = torch.nn.Linear(d_model_size, d_model_size)
        self.pruned_heads = set()

    def prune_heads(self, heads):
        attention_head_size = self.d_model_size // self.num_heads
        if len(heads) == 0:
        heads, index = find_pruneable_heads_and_indices(heads, self.num_heads, attention_head_size, self.pruned_heads)

        # Prune linear layers
        self.Wq = prune_linear_layer(self.Wq, index)
        self.Wk = prune_linear_layer(self.Wk, index)
        self.Wv = prune_linear_layer(self.Wv, index)
        self.dense = prune_linear_layer(self.dense, index, dim=1)

        # Update hyper params
        self.num_heads = self.num_heads - len(heads)
        self.d_model_size = attention_head_size * self.num_heads
        self.pruned_heads = self.pruned_heads.union(heads)

    def split_into_heads(self, x, batch_size):
        x = x.reshape(batch_size, -1, self.num_heads, self.depth)
        return x.permute([0, 2, 1, 3])

    def forward(
        batch_size = q.shape[0]

        q = self.Wq(q)
        k = self.Wk(k)
        v = self.Wv(v)

        q = self.split_into_heads(q, batch_size)
        k = self.split_into_heads(k, batch_size)
        v = self.split_into_heads(v, batch_size)
        if layer_past is not None:
            past_key, past_value = layer_past[0], layer_past[1]
            k =, k), dim=-2)
            v =, v), dim=-2)

        if use_cache is True:
            present = torch.stack((k, v))
            present = (None,)

        output = scaled_dot_product_attention(q, k, v, mask, attention_mask, head_mask)
        scaled_attention = output[0].permute([0, 2, 1, 3])
        attn = output[1]
        original_size_attention = scaled_attention.reshape(batch_size, -1, self.d_model_size)
        output = self.dense(original_size_attention)

        outputs = (output, present)
        if output_attentions:
            outputs = outputs + (attn,)
        return outputs

def point_wise_feed_forward_network(d_model_size, dff):
    return torch.nn.Sequential(torch.nn.Linear(d_model_size, dff), torch.nn.ReLU(), torch.nn.Linear(dff, d_model_size))

class EncoderLayer(torch.nn.Module):
    def __init__(self, d_model_size, num_heads, dff, rate=0.1):

        self.multi_head_attention = MultiHeadAttention(d_model_size, num_heads)
        self.ffn = point_wise_feed_forward_network(d_model_size, dff)

        self.layernorm1 = torch.nn.LayerNorm(d_model_size, eps=1e-6)
        self.layernorm2 = torch.nn.LayerNorm(d_model_size, eps=1e-6)

        self.dropout1 = torch.nn.Dropout(rate)
        self.dropout2 = torch.nn.Dropout(rate)

    def forward(
        self, x, mask, layer_past=None, attention_mask=None, head_mask=None, use_cache=False, output_attentions=False
        normed = self.layernorm1(x)
        attn_outputs = self.multi_head_attention(
        attn_output = attn_outputs[0]
        attn_output = self.dropout1(attn_output)
        out1 = x + attn_output

        out2 = self.layernorm2(out1)
        ffn_output = self.ffn(out2)
        ffn_output = self.dropout2(ffn_output)
        out2 = out1 + ffn_output

        outputs = (out2,) + attn_outputs[1:]
        return outputs

class CTRLPreTrainedModel(PreTrainedModel):
    """An abstract class to handle weights initialization and
    a simple interface for downloading and loading pretrained models.

    config_class = CTRLConfig
    base_model_prefix = "transformer"

    def _init_weights(self, module):
        """Initialize the weights."""
        if isinstance(module, (nn.Linear, nn.Embedding, Conv1D)):
            # Slightly different from the TF version which uses truncated_normal for initialization
            # cf
  , std=self.config.initializer_range)
            if isinstance(module, (nn.Linear, Conv1D)) and module.bias is not None:
        elif isinstance(module, nn.LayerNorm):


    This model inherits from :class:`~transformers.PreTrainedModel`. Check the superclass documentation for the generic
    methods the library implements for all its model (such as downloading or saving, resizing the input embeddings,
    pruning heads etc.)

    This model is also a PyTorch `torch.nn.Module <>`__ subclass.
    Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general
    usage and behavior.

        config (:class:`~transformers.CTRLConfig`): Model configuration class with all the parameters of the model.
            Initializing with a config file does not load the weights associated with the model, only the configuration.
            Check out the :meth:`~transformers.PreTrainedModel.from_pretrained` method to load the model weights.

        input_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`):
            :obj:`input_ids_length` = ``sequence_length`` if ``past_key_values`` is ``None`` else
            ``past_key_values[0].shape[-2]`` (``sequence_length`` of input past key value states).
            Indices of input sequence tokens in the vocabulary.

            If ``past_key_values`` is used, only input IDs that do not have their past calculated should be passed as

            Indices can be obtained using :class:`~transformers.CTRLTokenizer`.
            See :meth:`transformers.PreTrainedTokenizer.__call__` and
            :meth:`transformers.PreTrainedTokenizer.encode` for details.

            `What are input IDs? <../glossary.html#input-ids>`__
        past_key_values (:obj:`List[torch.FloatTensor]` of length :obj:`config.n_layers`):
            Contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
            (see ``past_key_values`` output below). Can be used to speed up sequential decoding.
            The ``input_ids`` which have their past given to this model should not be passed as input ids as they have
            already been computed.
        attention_mask (:obj:`torch.FloatTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
            Mask to avoid performing attention on padding token indices.
            Mask values selected in ``[0, 1]``:

            - 1 for tokens that are **not masked**,
            - 0 for tokens that are **maked**.

            `What are attention masks? <../glossary.html#attention-mask>`__
        token_type_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
            Segment token indices to indicate first and second portions of the inputs.
            Indices are selected in ``[0, 1]``:

            - 0 corresponds to a `sentence A` token,
            - 1 corresponds to a `sentence B` token.

            `What are token type IDs? <../glossary.html#token-type-ids>`_
        position_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
            Indices of positions of each input sequence tokens in the position embeddings.
            Selected in the range ``[0, config.max_position_embeddings - 1]``.

            `What are position IDs? <../glossary.html#position-ids>`_
        head_mask (:obj:`torch.FloatTensor` of shape :obj:`(num_heads,)` or :obj:`(num_layers, num_heads)`, `optional`):
            Mask to nullify selected heads of the self-attention modules.
            Mask values selected in ``[0, 1]``:

            - 1 indicates the head is **not masked**,
            - 0 indicates the head is **masked**.

        inputs_embeds (:obj:`torch.FloatTensor` of shape :obj:`(batch_size, sequence_length, hidden_size)`, `optional`):
            Optionally, instead of passing :obj:`input_ids` you can choose to directly pass an embedded representation.
            This is useful if you want more control over how to convert :obj:`input_ids` indices into associated
            vectors than the model's internal embedding lookup matrix.
        use_cache (:obj:`bool`, `optional`):
            If set to :obj:`True`, ``past_key_values`` key value states are returned and can be used to speed up
            decoding (see ``past_key_values``).
        output_attentions (:obj:`bool`, `optional`):
            Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
            tensors for more detail.
        output_hidden_states (:obj:`bool`, `optional`):
            Whether or not to return the hidden states of all layers. See ``hidden_states`` under returned tensors for
            more detail.
        return_dict (:obj:`bool`, `optional`):
            Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.

[docs]@add_start_docstrings( "The bare CTRL Model transformer outputting raw hidden-states without any specific head on top.", CTRL_START_DOCSTRING, ) class CTRLModel(CTRLPreTrainedModel): def __init__(self, config): super().__init__(config) self.d_model_size = config.n_embd self.num_layers = config.n_layer self.pos_encoding = positional_encoding(config.n_positions, self.d_model_size, torch.float) self.w = nn.Embedding(config.vocab_size, config.n_embd) self.dropout = nn.Dropout(config.embd_pdrop) self.h = nn.ModuleList( [EncoderLayer(config.n_embd, config.n_head, config.dff, config.resid_pdrop) for _ in range(config.n_layer)] ) self.layernorm = nn.LayerNorm(config.n_embd, eps=config.layer_norm_epsilon) self.init_weights() def get_input_embeddings(self): return self.w def set_input_embeddings(self, new_embeddings): self.w = new_embeddings def _prune_heads(self, heads_to_prune): """Prunes heads of the model. heads_to_prune: dict of {layer_num: list of heads to prune in this layer} """ for layer, heads in heads_to_prune.items(): self.h[layer].multi_head_attention.prune_heads(heads)
[docs] @add_start_docstrings_to_callable(CTRL_INPUTS_DOCSTRING) @add_code_sample_docstrings( tokenizer_class=_TOKENIZER_FOR_DOC, checkpoint="ctrl", output_type=BaseModelOutputWithPast, config_class=_CONFIG_FOR_DOC, ) def forward( self, input_ids=None, past_key_values=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None, use_cache=None, output_attentions=None, output_hidden_states=None, return_dict=None, **kwargs, ): if "past" in kwargs: warnings.warn( "The `past` argument is deprecated and will be removed in a future version, use `past_key_values` instead.", FutureWarning, ) past_key_values = kwargs.pop("past") assert kwargs == {}, f"Unexpected keyword arguments: {list(kwargs.keys())}." output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions use_cache = use_cache if use_cache is not None else self.config.use_cache output_hidden_states = ( output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states ) return_dict = return_dict if return_dict is not None else self.config.use_return_dict if input_ids is not None and inputs_embeds is not None: raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time") elif input_ids is not None: input_shape = input_ids.size() input_ids = input_ids.view(-1, input_shape[-1]) batch_size = input_ids.shape[0] elif inputs_embeds is not None: input_shape = inputs_embeds.size()[:-1] batch_size = inputs_embeds.shape[0] else: raise ValueError("You have to specify either input_ids or inputs_embeds") if past_key_values is None: past_length = 0 past_key_values = [None] * len(self.h) else: past_length = past_key_values[0][0].size(-2) if position_ids is None: device = input_ids.device if input_ids is not None else inputs_embeds.device position_ids = torch.arange(past_length, input_shape[-1] + past_length, dtype=torch.long, device=device) position_ids = position_ids.unsqueeze(0).view(-1, input_shape[-1]) # Attention mask. if attention_mask is not None: assert batch_size > 0, "batch_size has to be defined and > 0" attention_mask = attention_mask.view(batch_size, -1) # We create a 3D attention mask from a 2D tensor mask. # Sizes are [batch_size, 1, 1, to_seq_length] # So we can broadcast to [batch_size, num_heads, from_seq_length, to_seq_length] # this attention mask is more simple than the triangular masking of causal attention # used in OpenAI GPT, we just need to prepare the broadcast dimension here. attention_mask = attention_mask.unsqueeze(1).unsqueeze(2) # Since attention_mask is 1.0 for positions we want to attend and 0.0 for # masked positions, this operation will create a tensor which is 0.0 for # positions we want to attend and -10000.0 for masked positions. # Since we are adding it to the raw scores before the softmax, this is # effectively the same as removing these entirely. attention_mask = # fp16 compatibility attention_mask = (1.0 - attention_mask) * -10000.0 # Prepare head mask if needed head_mask = self.get_head_mask(head_mask, self.config.n_layer) if token_type_ids is not None: token_type_ids = token_type_ids.view(-1, input_shape[-1]) token_type_embeds = self.w(token_type_ids) token_type_embeds *= np.sqrt(self.d_model_size) else: token_type_embeds = 0 position_ids = position_ids.view(-1, input_shape[-1]) if inputs_embeds is None: inputs_embeds = self.w(input_ids) # inputs_embeds = embedded.unsqueeze(0) if len(input_ids.shape)<2 else embedded seq_len = input_shape[-1] mask = torch.triu(torch.ones(seq_len + past_length, seq_len + past_length), 1).to(inputs_embeds.device) inputs_embeds *= np.sqrt(self.d_model_size) pos_embeds = self.pos_encoding[position_ids, :].to(inputs_embeds.device) hidden_states = inputs_embeds + pos_embeds + token_type_embeds hidden_states = self.dropout(hidden_states) output_shape = input_shape + (inputs_embeds.size(-1),) presents = () if use_cache else None all_hidden_states = () if output_hidden_states else None all_attentions = [] if output_attentions else None for i, (h, layer_past) in enumerate(zip(self.h, past_key_values)): if output_hidden_states: all_hidden_states = all_hidden_states + (hidden_states.view(*output_shape),) outputs = h( hidden_states, mask, layer_past=layer_past, attention_mask=attention_mask, head_mask=head_mask[i], use_cache=use_cache, output_attentions=output_attentions, ) hidden_states, present = outputs[:2] if use_cache is True: presents = presents + (present,) if output_attentions: all_attentions.append(outputs[2]) hidden_states = self.layernorm(hidden_states) hidden_states = hidden_states.view(*output_shape) if output_hidden_states: all_hidden_states = all_hidden_states + (hidden_states,) if output_attentions: # let the number of heads free (-1) so we can extract attention even after head pruning attention_output_shape = input_shape[:-1] + (-1,) + all_attentions[0].shape[-2:] all_attentions = tuple(t.view(*attention_output_shape) for t in all_attentions) if not return_dict: return tuple(v for v in [hidden_states, presents, all_hidden_states, all_attentions] if v is not None) return BaseModelOutputWithPast( last_hidden_state=hidden_states, past_key_values=presents, hidden_states=all_hidden_states, attentions=all_attentions, )
[docs]@add_start_docstrings( """The CTRL Model transformer with a language modeling head on top (linear layer with weights tied to the input embeddings). """, CTRL_START_DOCSTRING, ) class CTRLLMHeadModel(CTRLPreTrainedModel): def __init__(self, config): super().__init__(config) self.transformer = CTRLModel(config) self.lm_head = nn.Linear(config.n_embd, config.vocab_size, bias=True) self.init_weights() def get_output_embeddings(self): return self.lm_head def prepare_inputs_for_generation(self, input_ids, past, **kwargs): # only last token for inputs_ids if past is defined in kwargs if past: input_ids = input_ids[:, -1].unsqueeze(-1) return {"input_ids": input_ids, "past_key_values": past, "use_cache": kwargs["use_cache"]}
[docs] @add_start_docstrings_to_callable(CTRL_INPUTS_DOCSTRING) @add_code_sample_docstrings( tokenizer_class=_TOKENIZER_FOR_DOC, checkpoint="ctrl", output_type=CausalLMOutputWithPast, config_class=_CONFIG_FOR_DOC, ) def forward( self, input_ids=None, past_key_values=None, attention_mask=None, token_type_ids=None, position_ids=None, head_mask=None, inputs_embeds=None, labels=None, use_cache=None, output_attentions=None, output_hidden_states=None, return_dict=None, **kwargs, ): r""" labels (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`): Labels for language modeling. Note that the labels **are shifted** inside the model, i.e. you can set ``labels = input_ids`` Indices are selected in ``[-100, 0, ..., config.vocab_size]`` All labels set to ``-100`` are ignored (masked), the loss is only computed for labels in ``[0, ..., config.vocab_size]`` """ if "past" in kwargs: warnings.warn( "The `past` argument is deprecated and will be removed in a future version, use `past_key_values` instead.", FutureWarning, ) past_key_values = kwargs.pop("past") assert kwargs == {}, f"Unexpected keyword arguments: {list(kwargs.keys())}." return_dict = return_dict if return_dict is not None else self.config.use_return_dict transformer_outputs = self.transformer( input_ids, past_key_values=past_key_values, attention_mask=attention_mask, token_type_ids=token_type_ids, position_ids=position_ids, head_mask=head_mask, inputs_embeds=inputs_embeds, use_cache=use_cache, output_attentions=output_attentions, output_hidden_states=output_hidden_states, return_dict=return_dict, ) hidden_states = transformer_outputs[0] lm_logits = self.lm_head(hidden_states) loss = None if labels is not None: # Shift so that tokens < n predict n shift_logits = lm_logits[..., :-1, :].contiguous() shift_labels = labels[..., 1:].contiguous() # Flatten the tokens loss_fct = CrossEntropyLoss() loss = loss_fct(shift_logits.view(-1, shift_logits.size(-1)), shift_labels.view(-1)) if not return_dict: output = (lm_logits,) + transformer_outputs[1:] return ((loss,) + output) if loss is not None else output return CausalLMOutputWithPast( loss=loss, logits=lm_logits, past_key_values=transformer_outputs.past_key_values, hidden_states=transformer_outputs.hidden_states, attentions=transformer_outputs.attentions, )