181 lines
7.5 KiB
Python
181 lines
7.5 KiB
Python
# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
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# SPDX-License-Identifier: Apache-2.0
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# Adapt from https://github.com/NVIDIA/Megatron-LM/blob/b1efb3c7126ef7615e8c333432d76e08038e17ff/pretrain_gpt.py
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import argparse
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import inspect
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from contextlib import nullcontext
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from typing import Literal
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import torch
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from megatron.core import tensor_parallel
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from megatron.core.models.gpt import GPTModel
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from megatron.core.models.gpt.gpt_layer_specs import (
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get_gpt_decoder_block_spec,
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get_gpt_layer_local_spec,
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get_gpt_layer_with_transformer_engine_spec,
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)
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from megatron.core.transformer.spec_utils import import_module
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from megatron.core.transformer.transformer_config import TransformerConfig
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from megatron.training.arguments import core_transformer_config_from_args
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# Adapt from https://github.com/volcengine/verl/blob/c3b20575d2bc815fcccd84bddb4c0401fc4b632b/verl/models/llama/megatron/layers/parallel_linear.py#L82
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class LinearForLastLayer(torch.nn.Linear):
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def __init__(
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self,
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input_size: int,
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output_size: int,
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*,
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config: TransformerConfig,
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bias: bool = True,
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) -> None:
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super().__init__(in_features=input_size, out_features=output_size, bias=bias)
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self.sequence_parallel = config.sequence_parallel
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if self.sequence_parallel:
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self.weight.sequence_parallel = True
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self.weight.data.normal_(mean=0.0, std=0.02)
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if bias:
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self.bias.data.zero_()
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def forward(
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self,
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input_: torch.Tensor,
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weight: torch.Tensor | None = None,
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runtime_gather_output: bool | None = None,
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) -> tuple[torch.Tensor, None]:
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logits = super().forward(input_)
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logits = logits.float()
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if self.sequence_parallel:
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logits = tensor_parallel.gather_from_sequence_parallel_region(logits, tensor_parallel_output_grad=False)
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return logits, None
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def get_model_provider_func(
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args: argparse.Namespace,
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role: Literal["actor", "critic"] = "actor",
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):
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if args.megatron_to_hf_mode == "bridge":
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from megatron.bridge import AutoBridge
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bridge = AutoBridge.from_hf_pretrained(args.hf_checkpoint, trust_remote_code=True)
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provider = bridge.to_megatron_provider(load_weights=False)
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# TODO: we should not manually set this...
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provider.tensor_model_parallel_size = args.tensor_model_parallel_size
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provider.pipeline_model_parallel_size = args.pipeline_model_parallel_size
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provider.expert_model_parallel_size = args.expert_model_parallel_size
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provider.expert_tensor_parallel_size = args.expert_tensor_parallel_size
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provider.sequence_parallel = args.sequence_parallel
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provider.finalize()
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return provider.provide
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def model_provider(pre_process: bool = True, post_process: bool = True, vp_stage: int | None = None) -> GPTModel:
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"""Builds the model.
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If you set the use_legacy_models to True, it will return the legacy GPT model and if not the mcore GPT model.
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Args:
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pre_process (bool, optional): Set to true if you need to compute embedings. Defaults to True.
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post_process (bool, optional): Set to true if you need to want to compute output logits/loss. Defaults to True.
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Returns:
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Union[GPTModel, megatron.legacy.model.GPTModel]: The returned model
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"""
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use_te = args.transformer_impl == "transformer_engine"
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# Experimental loading arguments from yaml
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config: TransformerConfig = core_transformer_config_from_args(args)
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if args.spec is not None:
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transformer_layer_spec = import_module(args.spec)
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# Allow the spec to be a function so that user can use customized Megatron easier.
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if callable(transformer_layer_spec):
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transformer_layer_spec = transformer_layer_spec(args, config, vp_stage)
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else:
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if args.num_experts:
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# Define the decoder block spec
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kwargs = {
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"use_transformer_engine": use_te,
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}
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if vp_stage is not None:
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kwargs["vp_stage"] = vp_stage
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transformer_layer_spec = get_gpt_decoder_block_spec(config, **kwargs)
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else:
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# Define the decoder layer spec
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if use_te:
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transformer_layer_spec = get_gpt_layer_with_transformer_engine_spec(
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num_experts=args.num_experts,
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moe_grouped_gemm=args.moe_grouped_gemm,
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qk_layernorm=args.qk_layernorm,
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multi_latent_attention=args.multi_latent_attention,
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moe_use_legacy_grouped_gemm=args.moe_use_legacy_grouped_gemm,
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)
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else:
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transformer_layer_spec = get_gpt_layer_local_spec(
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num_experts=args.num_experts,
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moe_grouped_gemm=args.moe_grouped_gemm,
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qk_layernorm=args.qk_layernorm,
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multi_latent_attention=args.multi_latent_attention,
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moe_use_legacy_grouped_gemm=args.moe_use_legacy_grouped_gemm,
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)
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build_model_context = nullcontext
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build_model_context_args = {}
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if args.fp8_param_gather:
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try:
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from transformer_engine.pytorch import fp8_model_init
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build_model_context = fp8_model_init
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build_model_context_args["enabled"] = True
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# Check if fp8_model_init supports preserve_high_precision_init_val
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if "preserve_high_precision_init_val" in inspect.signature(fp8_model_init).parameters:
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build_model_context_args["preserve_high_precision_init_val"] = True
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except Exception as e:
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raise RuntimeError(
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"--fp8-param-gather requires `fp8_model_init` from TransformerEngine, but not found."
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) from e
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kwargs = {
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"config": config,
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"transformer_layer_spec": transformer_layer_spec,
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"vocab_size": args.padded_vocab_size,
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"max_sequence_length": args.max_position_embeddings,
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"pre_process": pre_process,
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"post_process": post_process,
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"fp16_lm_cross_entropy": args.fp16_lm_cross_entropy,
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"parallel_output": True,
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"share_embeddings_and_output_weights": not args.untie_embeddings_and_output_weights,
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"position_embedding_type": args.position_embedding_type,
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"rotary_percent": args.rotary_percent,
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"rotary_base": args.rotary_base,
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"rope_scaling": args.use_rope_scaling,
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}
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if vp_stage is not None:
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kwargs["vp_stage"] = vp_stage
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if args.mtp_num_layers:
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from megatron.core.models.gpt.gpt_layer_specs import get_gpt_mtp_block_spec
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mtp_kwargs = {
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"use_transformer_engine": use_te,
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}
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if vp_stage is not None:
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mtp_kwargs["vp_stage"] = vp_stage
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mtp_block_spec = get_gpt_mtp_block_spec(config, transformer_layer_spec, **mtp_kwargs)
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kwargs["mtp_block_spec"] = mtp_block_spec
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with build_model_context(**build_model_context_args):
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model = GPTModel(**kwargs)
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if post_process and role == "critic":
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model.output_layer = LinearForLastLayer(input_size=config.hidden_size, output_size=1, config=config)
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return model
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return model_provider
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