xc-llm-ascend/vllm_ascend/models/deepseek_mtp.py

#
# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
# Adapted from vllm/model_executor/models/qwen2_vl.py
# Copyright 2023 The vLLM team.
#
# This file is a part of the vllm-ascend project.
#
# 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
#
# 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
# limitations under the License.

from typing import List, Optional

import torch
import torch.nn as nn
from transformers import PretrainedConfig
from vllm.attention.backends.abstract import AttentionMetadata
from vllm.config import CacheConfig, ModelConfig, VllmConfig
from vllm.model_executor.layers.layernorm import RMSNorm
from vllm.model_executor.layers.logits_processor import LogitsProcessor
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.layers.sampler import get_sampler
from vllm.model_executor.layers.vocab_parallel_embedding import \
    VocabParallelEmbedding
from vllm.model_executor.models.deepseek_mtp import (
    DeepSeekMTP, DeepSeekMultiTokenPredictor, DeepSeekMultiTokenPredictorLayer,
    SharedHead)
from vllm.model_executor.models.utils import maybe_prefix
from vllm.model_executor.sampling_metadata import SamplingMetadata

from .deepseek_v2 import CustomDeepseekV2DecoderLayer


class CustomDeepSeekMultiTokenPredictorLayer(DeepSeekMultiTokenPredictorLayer):

    def __init__(
        self,
        config: PretrainedConfig,
        prefix: str,
        model_config: ModelConfig,
        cache_config: Optional[CacheConfig] = None,
        quant_config: Optional[QuantizationConfig] = None,
    ) -> None:
        nn.Module.__init__(self)
        self.embed_tokens = VocabParallelEmbedding(
            config.vocab_size,
            config.hidden_size,
        )

        self.enorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.hnorm = RMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.eh_proj = nn.Linear(config.hidden_size * 2,
                                 config.hidden_size,
                                 bias=False)
        self.shared_head = SharedHead(config=config, quant_config=quant_config)
        self.mtp_block = CustomDeepseekV2DecoderLayer(config, prefix,
                                                      model_config,
                                                      cache_config,
                                                      quant_config)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        kv_cache: torch.Tensor,
        attn_metadata: AttentionMetadata,
        previous_hidden_states: torch.Tensor,
        inputs_embeds: Optional[torch.Tensor] = None,
        spec_step_index: int = 0,
    ) -> torch.Tensor:
        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids)
        assert inputs_embeds is not None
        # masking inputs at position 0, as not needed by MTP
        inputs_embeds = torch.where((positions == 0).unsqueeze(-1),
                                    torch.zeros_like(inputs_embeds),
                                    inputs_embeds)
        inputs_embeds = self.enorm(inputs_embeds)
        previous_hidden_states = self.hnorm(previous_hidden_states)

        hidden_states = self.eh_proj(
            torch.cat([inputs_embeds, previous_hidden_states], dim=-1))

        hidden_states, residual = self.mtp_block(positions=positions,
                                                 hidden_states=hidden_states,
                                                 kv_cache=kv_cache,
                                                 attn_metadata=attn_metadata,
                                                 residual=None)
        hidden_states = residual + hidden_states
        return hidden_states


class CustomDeepSeekMultiTokenPredictor(DeepSeekMultiTokenPredictor):

    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        nn.Module.__init__(self)
        config = vllm_config.model_config.hf_config
        self.mtp_start_layer_idx = config.num_hidden_layers
        self.num_mtp_layers = config.num_nextn_predict_layers
        # to map the exact layer index from weights
        self.layers = torch.nn.ModuleDict({
            str(idx): CustomDeepSeekMultiTokenPredictorLayer(
                config,
                f"{prefix}.layers.{idx}",
                model_config=vllm_config.model_config,
                cache_config=vllm_config.cache_config,
                quant_config=vllm_config.quant_config,
            )
            for idx in range(self.mtp_start_layer_idx,
                             self.mtp_start_layer_idx + self.num_mtp_layers)
        })

        # Note: torch._dynamo.exc.Unsupported: builtin: str
        self.layers_list = [
            self.layers[str(idx)]
            for idx in range(self.mtp_start_layer_idx,
                             self.mtp_start_layer_idx + self.num_mtp_layers)
        ]
        self.logits_processor = LogitsProcessor(config.vocab_size)

    def forward(
        self,
        input_ids: torch.Tensor,
        positions: torch.Tensor,
        kv_caches: List[torch.Tensor],
        attn_metadata: AttentionMetadata,
        previous_hidden_states: torch.Tensor,
        inputs_embeds: Optional[torch.Tensor] = None,
        spec_step_idx: int = 0,
    ) -> torch.Tensor:
        current_step_idx = (spec_step_idx % self.num_mtp_layers)
        return self.layers_list[current_step_idx](
            input_ids,
            positions,
            kv_caches[current_step_idx],
            attn_metadata,
            previous_hidden_states,
            inputs_embeds,
            current_step_idx,
        )

    def compute_logits(
        self,
        hidden_states: torch.Tensor,
        sampling_metadata: SamplingMetadata,
        spec_step_idx: int = 0,
    ) -> torch.Tensor:
        current_step_idx = (spec_step_idx % self.num_mtp_layers)
        mtp_layer = self.layers_list[current_step_idx]
        logits = self.logits_processor(mtp_layer.shared_head.head,
                                       mtp_layer.shared_head(hidden_states),
                                       sampling_metadata)
        return logits


class CustomDeepSeekMTP(DeepSeekMTP):

    def __init__(self, *, vllm_config: VllmConfig, prefix: str = ""):
        nn.Module.__init__(self)
        self.config = vllm_config.model_config.hf_config
        self.model = CustomDeepSeekMultiTokenPredictor(vllm_config=vllm_config,
                                                       prefix=maybe_prefix(
                                                           prefix, "model"))

        self.sampler = get_sampler()