# SPDX-FileCopyrightText: Copyright (c) 2022-2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# 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 tensorrt_llm.models.llama.model import LLaMAForCausalLM
from tensorrt_llm.models.qwen.model import QWenForCausalLM
from ..._common import default_net
from ..._utils import pad_vocab_size
from ...functional import ACT2FN, stack
from ...layers import ColumnLinear
from ...mapping import Mapping
from ...module import Module, ModuleList
from ..modeling_utils import PretrainedModel
from .config import MedusaConfig
class MedusaLayer(Module):
def __init__(
self,
hidden_size,
hidden_act="silu",
dtype=None,
mapping=Mapping(),
):
super().__init__()
self.linear = ColumnLinear(hidden_size,
hidden_size,
dtype=dtype,
tp_group=mapping.tp_group,
tp_size=mapping.tp_size,
gather_output=True)
self.hidden_act = hidden_act
def forward(self, x):
return x + ACT2FN[self.hidden_act](self.linear(x))
class MedusaHead(Module):
def __init__(
self,
num_layers,
hidden_size,
vocab_size,
hidden_act="silu",
dtype=None,
mapping=Mapping(),
):
super().__init__()
self.medusa_layers = ModuleList([
MedusaLayer(hidden_size=hidden_size,
hidden_act=hidden_act,
dtype=dtype,
mapping=mapping) for _ in range(num_layers)
])
self.lm_head = ColumnLinear(hidden_size,
vocab_size,
bias=False,
dtype=dtype,
tp_group=mapping.tp_group,
tp_size=mapping.tp_size,
gather_output=True)
return
def forward(self, x):
hidden_states = x
for layer in self.medusa_layers:
hidden_states = layer(hidden_states)
return self.lm_head(hidden_states)
# MedusaForCausalLm is a thin wrapper that picks parent class for GenericMedusaForCausalLM.
# All medusa functionality is defined in GenericMedusaForCausalLM.
[docs]
class MedusaForCausalLm(PretrainedModel):
config_class = MedusaConfig
def __init__(self, config: MedusaConfig):
super().__init__(config)
BaseLM = QWenForCausalLM if "qwen" in config.model_type else LLaMAForCausalLM
class GenericMedusaForCausalLM(BaseLM):
def __init__(self, config: MedusaConfig):
super().__init__(config)
self.num_medusa_heads = config.num_medusa_heads
self.num_medusa_layers = config.num_medusa_layers
self.hidden_size = config.hidden_size
self.vocab_size = config.vocab_size
vocab_size_padded = pad_vocab_size(self.vocab_size,
config.mapping.tp_size)
self.medusa_heads = ModuleList([
MedusaHead(num_layers=self.num_medusa_layers,
hidden_size=config.hidden_size,
vocab_size=vocab_size_padded,
hidden_act=config.hidden_act,
dtype=config.dtype,
mapping=config.mapping)
for _ in range(self.num_medusa_heads)
])
self.max_medusa_token_len = config.max_draft_len
def forward(self, *args, **kwargs):
output_original = True
hidden_states = super().forward(*args, **kwargs)
if kwargs['use_cache']:
if default_net().plugin_config.paged_kv_cache:
lm_logits, hidden_states, _ = hidden_states
else:
lm_logits, presents, hidden_states = hidden_states
if self.mapping.is_last_pp_rank():
medusa_logits = []
for i in range(self.num_medusa_heads):
medusa_logits.append(
self.medusa_heads[i](hidden_states))
# [num_medusa_heads, batch_size, num_medusa_tokens + 1, padded_vocab_size].
# Remove padding [num_medusa_heads, batch_size * num_medusa_tokens + 1, padded_vocab_size].
medusa_logits = stack(medusa_logits, dim=0)
medusa_logits.mark_output('medusa_logits',
self.config.logits_dtype)
else:
hidden_states.mark_output('hidden_states_output',
self.config.dtype)
if kwargs['use_cache'] and default_net(
).plugin_config.paged_kv_cache == False:
if self.mapping.is_last_pp_rank():
if output_original:
return (medusa_logits, lm_logits, presents)
return (medusa_logits, presents)
return (hidden_states, presents)
else:
if self.mapping.is_last_pp_rank():
if output_original:
return medusa_logits, lm_logits
return medusa_logits
return hidden_states
def prepare_inputs(self, *args, **kwargs):
kwargs['speculative_decoding_draft_tokens_external'] = False
kwargs['max_draft_len'] = self.max_medusa_token_len
return super().prepare_inputs(*args, **kwargs)
self.model = GenericMedusaForCausalLM(config)
# Specialization to redirect accesses to self.model
def __getattribute__(self, name):
if name == 'model' or '__' in name:
return object.__getattribute__(self, name)
else:
model = object.__getattribute__(self, 'model')
return model.__getattribute__(name)
# Override specialized __setattr__ defined in Module
def __setattr__(self, name, value) -> None:
object.__setattr__(self, name, value)