# Copyright (c) 2022, NVIDIA CORPORATION. All rights reserved. """BERT Style dataset.""" import numpy as np import torch from megatron import ( get_args, get_tokenizer, mpu, print_rank_0 ) from megatron.data.dataset_utils import ( get_samples_mapping, get_a_and_b_segments, truncate_segments, create_tokens_and_tokentypes, create_masked_lm_predictions ) class BertDataset(torch.utils.data.Dataset): def __init__(self, name, indexed_dataset, data_prefix, num_epochs, max_num_samples, masked_lm_prob, max_seq_length, short_seq_prob, seed, binary_head): # Params to store. self.name = name self.seed = seed self.masked_lm_prob = masked_lm_prob self.max_seq_length = max_seq_length self.binary_head = binary_head # Dataset. self.indexed_dataset = indexed_dataset # Build the samples mapping. self.samples_mapping = get_samples_mapping(self.indexed_dataset, data_prefix, num_epochs, max_num_samples, self.max_seq_length - 3, # account for added tokens short_seq_prob, self.seed, self.name, self.binary_head) # Vocab stuff. tokenizer = get_tokenizer() self.vocab_id_list = list(tokenizer.inv_vocab.keys()) self.vocab_id_to_token_dict = tokenizer.inv_vocab self.cls_id = tokenizer.cls self.sep_id = tokenizer.sep self.mask_id = tokenizer.mask self.pad_id = tokenizer.pad def __len__(self): return self.samples_mapping.shape[0] def __getitem__(self, idx): args = get_args() start_idx, end_idx, seq_length = self.samples_mapping[idx] sample = [self.indexed_dataset[i] for i in range(start_idx, end_idx)] # Note that this rng state should be numpy and not python since # python randint is inclusive whereas the numpy one is exclusive. # We % 2**32 since numpy requres the seed to be between 0 and 2**32 - 1 np_rng = np.random.RandomState(seed=((self.seed + idx) % 2**32)) train_sample = build_training_sample(sample, seq_length, self.max_seq_length, # needed for padding self.vocab_id_list, self.vocab_id_to_token_dict, self.cls_id, self.sep_id, self.mask_id, self.pad_id, self.masked_lm_prob, np_rng, self.binary_head) if args.return_data_index: train_sample['index'] = np.array([idx], dtype=np.int64) return train_sample def build_training_sample(sample, target_seq_length, max_seq_length, vocab_id_list, vocab_id_to_token_dict, cls_id, sep_id, mask_id, pad_id, masked_lm_prob, np_rng, binary_head): """Biuld training sample. Arguments: sample: A list of sentences in which each sentence is a list token ids. target_seq_length: Desired sequence length. max_seq_length: Maximum length of the sequence. All values are padded to this length. vocab_id_list: List of vocabulary ids. Used to pick a random id. vocab_id_to_token_dict: A dictionary from vocab ids to text tokens. cls_id: Start of example id. sep_id: Separator id. mask_id: Mask token id. pad_id: Padding token id. masked_lm_prob: Probability to mask tokens. np_rng: Random number genenrator. Note that this rng state should be numpy and not python since python randint is inclusive for the opper bound whereas the numpy one is exclusive. """ if binary_head: # We assume that we have at least two sentences in the sample assert len(sample) > 1 assert target_seq_length <= max_seq_length # Divide sample into two segments (A and B). if binary_head: tokens_a, tokens_b, is_next_random = get_a_and_b_segments(sample, np_rng) else: tokens_a = [] for j in range(len(sample)): tokens_a.extend(sample[j]) tokens_b = [] is_next_random = False # Truncate to `target_sequence_length`. max_num_tokens = target_seq_length truncated = truncate_segments(tokens_a, tokens_b, len(tokens_a), len(tokens_b), max_num_tokens, np_rng) # Build tokens and toketypes. tokens, tokentypes = create_tokens_and_tokentypes(tokens_a, tokens_b, cls_id, sep_id) # Masking. max_predictions_per_seq = masked_lm_prob * max_num_tokens (tokens, masked_positions, masked_labels, _, _) = create_masked_lm_predictions( tokens, vocab_id_list, vocab_id_to_token_dict, masked_lm_prob, cls_id, sep_id, mask_id, max_predictions_per_seq, np_rng) # Padding. tokens_np, tokentypes_np, labels_np, padding_mask_np, loss_mask_np \ = pad_and_convert_to_numpy(tokens, tokentypes, masked_positions, masked_labels, pad_id, max_seq_length) train_sample = { 'text': tokens_np, 'types': tokentypes_np, 'labels': labels_np, 'is_random': int(is_next_random), 'loss_mask': loss_mask_np, 'padding_mask': padding_mask_np, 'truncated': int(truncated)} return train_sample def pad_and_convert_to_numpy(tokens, tokentypes, masked_positions, masked_labels, pad_id, max_seq_length): """Pad sequences and convert them to numpy.""" # Some checks. num_tokens = len(tokens) padding_length = max_seq_length - num_tokens assert padding_length >= 0, \ f"num_tokens ({num_tokens}) is greater than " \ "max_seq_length ({max_seq_length})." assert len(tokentypes) == num_tokens assert len(masked_positions) == len(masked_labels) # Tokens and token types. filler = [pad_id] * padding_length tokens_np = np.array(tokens + filler, dtype=np.int64) tokentypes_np = np.array(tokentypes + filler, dtype=np.int64) # Padding mask. padding_mask_np = np.array([1] * num_tokens + [0] * padding_length, dtype=np.int64) # Lables and loss mask. labels = [-1] * max_seq_length loss_mask = [0] * max_seq_length for i in range(len(masked_positions)): assert masked_positions[i] < num_tokens labels[masked_positions[i]] = masked_labels[i] loss_mask[masked_positions[i]] = 1 labels_np = np.array(labels, dtype=np.int64) loss_mask_np = np.array(loss_mask, dtype=np.int64) return tokens_np, tokentypes_np, labels_np, padding_mask_np, loss_mask_np