XLM-R conversion

convert_roberta_original_pytorch_checkpoint_to_pytorch.py

# coding=utf-8
# Copyright 2018 The HuggingFace Inc. team.
#
# 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
#
#     http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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"""Convert RoBERTa checkpoint."""

from __future__ import absolute_import, division, print_function

import argparse
import logging
import numpy as np
import torch
import pathlib

from fairseq.models.roberta import RobertaModel as FairseqRobertaModel
from fairseq.modules import TransformerSentenceEncoderLayer
from transformers.modeling_bert import (BertConfig, BertEncoder,
                                        BertIntermediate, BertLayer,
                                        BertModel, BertOutput,
                                        BertSelfAttention,
                                        BertSelfOutput)
from transformers.modeling_roberta import (RobertaEmbeddings,
                                           RobertaForMaskedLM,
                                           RobertaForSequenceClassification,
                                           RobertaModel)

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

SAMPLE_TEXT = 'Hello world! cécé herlolip'


def convert_roberta_checkpoint_to_pytorch(roberta_checkpoint_path, pytorch_dump_folder_path, classification_head):
    """
    Copy/paste/tweak roberta's weights to our BERT structure.
    """
    roberta = FairseqRobertaModel.from_pretrained(roberta_checkpoint_path, bpe = 'sentencepiece')
    roberta.eval()  # disable dropout
    config = BertConfig(
        vocab_size_or_config_json_file=250002,
        hidden_size=roberta.args.encoder_embed_dim,
        num_hidden_layers=roberta.args.encoder_layers,
        num_attention_heads=roberta.args.encoder_attention_heads,
        intermediate_size=roberta.args.encoder_ffn_embed_dim,
        max_position_embeddings=514,
        type_vocab_size=1,
        layer_norm_eps=1e-5, # PyTorch default used in fairseq
    )
    if classification_head:
        config.num_labels = roberta.args.num_classes
    print("Our BERT config:", config)

    model = RobertaForSequenceClassification(config) if classification_head else RobertaForMaskedLM(config)
    model.eval()

    # Now let's copy all the weights.
    # Embeddings
    roberta_sent_encoder = roberta.model.decoder.sentence_encoder
    model.roberta.embeddings.word_embeddings.weight = roberta_sent_encoder.embed_tokens.weight
    model.roberta.embeddings.position_embeddings.weight = roberta_sent_encoder.embed_positions.weight
    model.roberta.embeddings.token_type_embeddings.weight.data = torch.zeros_like(model.roberta.embeddings.token_type_embeddings.weight)  # just zero them out b/c RoBERTa doesn't use them.
    model.roberta.embeddings.LayerNorm.weight = roberta_sent_encoder.emb_layer_norm.weight
    model.roberta.embeddings.LayerNorm.bias = roberta_sent_encoder.emb_layer_norm.bias

    for i in range(config.num_hidden_layers):
        # Encoder: start of layer
        layer: BertLayer = model.roberta.encoder.layer[i]
        roberta_layer: TransformerSentenceEncoderLayer = roberta_sent_encoder.layers[i]

        ### self attention
        self_attn: BertSelfAttention = layer.attention.self
        assert(
            roberta_layer.self_attn.k_proj.weight.data.shape == \
            roberta_layer.self_attn.q_proj.weight.data.shape == \
            roberta_layer.self_attn.v_proj.weight.data.shape == \
            torch.Size((config.hidden_size, config.hidden_size))
        )

        self_attn.query.weight.data = roberta_layer.self_attn.q_proj.weight
        self_attn.query.bias.data = roberta_layer.self_attn.q_proj.bias
        self_attn.key.weight.data = roberta_layer.self_attn.k_proj.weight
        self_attn.key.bias.data = roberta_layer.self_attn.k_proj.bias
        self_attn.value.weight.data = roberta_layer.self_attn.v_proj.weight
        self_attn.value.bias.data = roberta_layer.self_attn.v_proj.bias

        ### self-attention output
        self_output: BertSelfOutput = layer.attention.output
        assert(
            self_output.dense.weight.shape == roberta_layer.self_attn.out_proj.weight.shape
        )
        self_output.dense.weight = roberta_layer.self_attn.out_proj.weight
        self_output.dense.bias = roberta_layer.self_attn.out_proj.bias
        self_output.LayerNorm.weight = roberta_layer.self_attn_layer_norm.weight
        self_output.LayerNorm.bias = roberta_layer.self_attn_layer_norm.bias

        ### intermediate
        intermediate: BertIntermediate = layer.intermediate
        assert(
            intermediate.dense.weight.shape == roberta_layer.fc1.weight.shape
        )
        intermediate.dense.weight = roberta_layer.fc1.weight
        intermediate.dense.bias = roberta_layer.fc1.bias

        ### output
        bert_output: BertOutput = layer.output
        assert(
            bert_output.dense.weight.shape == roberta_layer.fc2.weight.shape
        )
        bert_output.dense.weight = roberta_layer.fc2.weight
        bert_output.dense.bias = roberta_layer.fc2.bias
        bert_output.LayerNorm.weight = roberta_layer.final_layer_norm.weight
        bert_output.LayerNorm.bias = roberta_layer.final_layer_norm.bias
        #### end of layer
    
    if classification_head:
        model.classifier.dense.weight = roberta.model.classification_heads['mnli'].dense.weight
        model.classifier.dense.bias = roberta.model.classification_heads['mnli'].dense.bias
        model.classifier.out_proj.weight = roberta.model.classification_heads['mnli'].out_proj.weight
        model.classifier.out_proj.bias = roberta.model.classification_heads['mnli'].out_proj.bias
    else:
        # LM Head
        model.lm_head.dense.weight = roberta.model.decoder.lm_head.dense.weight
        model.lm_head.dense.bias = roberta.model.decoder.lm_head.dense.bias
        model.lm_head.layer_norm.weight = roberta.model.decoder.lm_head.layer_norm.weight
        model.lm_head.layer_norm.bias = roberta.model.decoder.lm_head.layer_norm.bias
        model.lm_head.decoder.weight = roberta.model.decoder.lm_head.weight
        model.lm_head.bias = roberta.model.decoder.lm_head.bias

    # Let's check that we get the same results.
    input_ids: torch.Tensor = roberta.encode(SAMPLE_TEXT).unsqueeze(0) # batch of size 1

    our_output = model(input_ids)[0]
    if classification_head:
        their_output = roberta.model.classification_heads['mnli'](roberta.extract_features(input_ids))
    else:
        their_output = roberta.model(input_ids)[0]
    print(our_output.shape, their_output.shape)
    max_absolute_diff = torch.max(torch.abs(our_output - their_output)).item()
    print(f"max_absolute_diff = {max_absolute_diff}") # ~ 1e-7
    success = torch.allclose(our_output, their_output, atol=1e-3)
    print(
        "Do both models output the same tensors?",
        "🔥" if success else "💩"
    )
    if not success:
        raise Exception("Something went wRoNg")

    pathlib.Path(pytorch_dump_folder_path).mkdir(parents=True, exist_ok=True)
    print(f"Saving model to {pytorch_dump_folder_path}")
    model.save_pretrained(pytorch_dump_folder_path)


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    ## Required parameters
    parser.add_argument("--roberta_checkpoint_path",
                        default = None,
                        type = str,
                        required = True,
                        help = "Path the official PyTorch dump.")
    parser.add_argument("--pytorch_dump_folder_path",
                        default = None,
                        type = str,
                        required = True,
                        help = "Path to the output PyTorch model.")
    parser.add_argument("--classification_head",
                        action = "store_true",
                        help = "Whether to convert a final classification head.")
    args = parser.parse_args()
    convert_roberta_checkpoint_to_pytorch(
        args.roberta_checkpoint_path,
        args.pytorch_dump_folder_path,
        args.classification_head
    )