Add Megatron-LM pretrain function for the core.

Author: jaredcasper

pretrain_gpt_core.py

@@ -0,0 +1,127 @@
+# Copyright (c) 2022, NVIDIA CORPORATION.  All rights reserved.
+
+"""Pretrain GPT"""
+
+import torch
+from functools import partial
+from megatron import get_args
+from megatron.arguments import core_transformer_config_from_args
+from megatron import print_rank_0
+from megatron import get_timers
+from megatron import get_tokenizer
+from megatron.core import tensor_parallel
+from megatron.core.enums import ModelType
+from megatron.data.gpt_dataset import build_train_valid_test_datasets
+from megatron.core.models.gpt import GPTModel
+from megatron.training import pretrain
+from megatron.utils import get_ltor_masks_and_position_ids
+from megatron.utils import average_losses_across_data_parallel_group
+
+def model_provider(pre_process=True, post_process=True):
+    """Build the model."""
+
+    args = get_args()
+    config = core_transformer_config_from_args(args)
+
+    print_rank_0('building GPT model ...')
+    model = GPTModel(
+        config=config,
+        vocab_size=args.padded_vocab_size,
+        max_sequence_length=args.max_position_embeddings,
+        pre_process=pre_process,
+        post_process=post_process,
+        fp16_lm_cross_entropy=args.fp16_lm_cross_entropy,
+        parallel_output=True,
+        share_embeddings_and_output_weights=not args.untie_embeddings_and_output_weights
+    )
+    return model
+
+
+def get_batch(data_iterator):
+    """Generate a batch"""
+    args = get_args()
+    tokenizer = get_tokenizer()
+
+    # Items and their type.
+    keys = ['text']
+    datatype = torch.int64
+
+    # Broadcast data.
+    if data_iterator is not None:
+        data = next(data_iterator)
+    else:
+        data = None
+    data_b = tensor_parallel.broadcast_data(keys, data, datatype)
+
+    # Unpack.
+    tokens_ = data_b['text'].long()
+    labels = tokens_[:, 1:].contiguous()
+    tokens = tokens_[:, :-1].contiguous()
+
+    # Get the masks and postition ids.
+    attention_mask, loss_mask, position_ids = get_ltor_masks_and_position_ids(
+        tokens,
+        tokenizer.eod,
+        args.reset_position_ids,
+        args.reset_attention_mask,
+        args.eod_mask_loss)
+
+    return tokens, labels, loss_mask, attention_mask, position_ids
+
+def loss_func(loss_mask, output_tensor):
+    losses = output_tensor.float()
+    loss_mask = loss_mask.view(-1).float()
+    loss = torch.sum(losses.view(-1) * loss_mask) / loss_mask.sum()
+
+    # Reduce loss for logging.
+    averaged_loss = average_losses_across_data_parallel_group([loss])
+
+    return loss, {'lm loss': averaged_loss[0]}
+
+
+def forward_step(data_iterator, model):
+    """Forward step."""
+    args = get_args()
+    timers = get_timers()
+
+    # Get the batch.
+    timers('batch-generator', log_level=2).start()
+    tokens, labels, loss_mask, attention_mask, position_ids = get_batch(
+        data_iterator)
+    timers('batch-generator').stop()
+
+    output_tensor = model(tokens, position_ids, attention_mask,
+                          labels=labels)
+
+    return output_tensor, partial(loss_func, loss_mask)
+
+
+def train_valid_test_datasets_provider(train_val_test_num_samples):
+    """Build train, valid, and test datasets."""
+    args = get_args()
+
+    print_rank_0('> building train, validation, and test datasets '
+                 'for GPT ...')
+    train_ds, valid_ds, test_ds = build_train_valid_test_datasets(
+        data_prefix=args.data_path,
+        data_impl=args.data_impl,
+        splits_string=args.split,
+        train_valid_test_num_samples=train_val_test_num_samples,
+        seq_length=args.seq_length,
+        seed=args.seed,
+        skip_warmup=(not args.mmap_warmup),
+        train_data_prefix=args.train_data_path,
+        valid_data_prefix=args.valid_data_path,
+        test_data_prefix=args.test_data_path)
+    print_rank_0("> finished creating GPT datasets ...")
+
+    return train_ds, valid_ds, test_ds
+
+
+if __name__ == "__main__":
+
+    pretrain(train_valid_test_datasets_provider, model_provider,
+             ModelType.encoder_or_decoder,
+             forward_step,
+             args_defaults={'tokenizer_type': 'GPT2BPETokenizer'}
+    )