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Megatron Model Optimization and Deployment

Installation

We recommend that users follow TensorRT-LLM's official installation guide to build it from source and proceed with a containerized environment (docker.io/tensorrt_llm/release:latest):

git clone https://github.com/NVIDIA/TensorRT-LLM.git
cd TensorRT-LLM
git checkout v0.7.1
make -C docker release_build

TROUBLE SHOOTING: rather than copying each folder separately in docker/Dockerfile.multi, you may need to copy the entire dir as COPY ./ /src/tensorrt_llm since a git submodule is called later which requires .git to continue.

Once the container is built, install nvidia-ammo and additional dependencies for sharded checkpoint support:

pip install --no-cache-dir --extra-index-url https://pypi.nvidia.com nvidia-ammo
pip install zarr tensorstore==0.1.45

TensorRT-LLM quantization functionalities are currently packaged in nvidia-ammo. You can find more documentation about nvidia-ammo in TensorRT-LLM's quantization examples.

Support Matrix

The following matrix shows the current support for the PTQ + TensorRT-LLM export flow.

model fp16 int8_sq fp8 int4_awq
nextllm-2b x x x
nemotron3-8b x x
nemotron3-15b x x
llama2-text-7b x x x TP2
llama2-chat-70b x x x TP4

Our PTQ + TensorRT-LLM flow has native support on MCore GPTModel with a mixed layer spec (native ParallelLinear and Transformer-Engine Norm (TENorm). Note that this is not the default mcore gpt spec. You can still load the following checkpoint formats with some remedy:

GPTModel sharded remedy arguments
megatron.legacy.model --ammo-load-classic-megatron-to-mcore
TE-Fused (default mcore gpt spec) --ammo-convert-te-to-local-spec
TE-Fused (default mcore gpt spec) x

TROUBLE SHOOTING: If you are trying to load an unpacked .nemo sharded checkpoint, then typically you will need to adding additional_sharded_prefix="model." to ammo_load_checkpoint() since NeMo has an additional model. wrapper on top of the GPTModel.

NOTE: flag --ammo-load-classic-megatron-to-mcore may not work on all legacy checkpoint versions.

Examples

NOTE: we only provide a simple text generation script to test the generated TensorRT-LLM engines. For a production-level API server or enterprise support, see NeMo and TensorRT-LLM's backend for NVIDIA Triton Inference Server.

nemotron3-8B FP8 Quantization and TensorRT-LLM Deployment

First download the nemotron checkpoint from https://huggingface.co/nvidia/nemotron-3-8b-base-4k, extract the sharded checkpoint from the .nemo tarbal and fix the tokenizer file name.

NOTE: The following cloning method uses ssh, and assume you have registered the ssh-key in Hugging Face. If you are want to clone with https, then git clone https://huggingface.co/nvidia/nemotron-3-8b-base-4k with an access token.

git lfs install
git clone [email protected]:nvidia/nemotron-3-8b-base-4k
cd nemotron-3-8b-base-4k
tar -xvf Nemotron-3-8B-Base-4k.nemo
mv 586f3f51a9cf43bc9369bd53fa08868c_a934dc7c3e1e46a6838bb63379916563_3feba89c944047c19d5a1d0c07a85c32_mt_nlg_plus_multilingual_ja_zh_the_stack_frac_015_256k.model mt_nlg_plus_multilingual_ja_zh_the_stack_frac_015_256k.model
cd ..

Now launch the PTQ + TensorRT-LLM export script,

bash examples/inference/ptq_trtllm_nemotron3_8b ./nemotron-3-8b-base-4k None

By default, cnn_dailymail is used for calibration. The GPTModel will have quantizers for simulating the quantization effect. The checkpoint will be saved optionally (with quantizers as additional states) and can be restored for further evaluation. TensorRT-LLM engine is exported to /tmo/ammo by default.

The script expects ${CHECKPOINT_DIR} (./nemotron-3-8b-base-4k) to have the following structure:

├── model_weights
│   ├── common.pt
│   ...
│
├── model_config.yaml
├── mt_nlg_plus_multilingual_ja_zh_the_stack_frac_015_256k.model

NOTE: The script is using TP=8. Change $TP in the script if your checkpoint has a different tensor model parallelism.

KNOWN ISSUES: The mt_nlg_plus_multilingual_ja_zh_the_stack_frac_015_256k.model in the checkpoint is for Megatron-LM's GPTSentencePiece tokenizer. For TensorRT-LLM, we are trying to load this tokenizer as a Hugging Face T5Tokenizer by changing some special tokens, encode, and batch_decode. As a result, the tokenizer behavior in TensorRT-LLM engine may not match exactly.

TROUBLE SHOOTING: If you are loading .nemo sharded checkpoint here, call ammo_load_checkpoint(..., additional_sharded_prefix="model.") with additional sharded prefix in text_generation_ptq.py to align the sharded keys.

llama2-text-7b INT8 SmoothQuant and TensorRT-LLM Deployment

NOTE: Due to the LICENSE issue, we do not provide a MCore checkpoint to download. Users can follow the instruction in docs/llama2.md to convert the checkpoint to megatron classic GPTModel format and use --ammo-load-classic-megatron-to-mcore flag which will remap the checkpoint to the MCore GPTModel spec that we support.

bash examples/inference/ptq_trtllm_llama_7b.sh ${CHECKPOINT_DIR}

The script expect ${CHECKPOINT_DIR} to have the following structure:

├── hf
│   ├── tokenizer.config
│   ├── tokenizer.model
│   ...
│
├── iter_0000001
│   ├── mp_rank_00
│   ...
│
├── latest_checkpointed_iteration.txt

In short, other than the converted llama megatron checkpoint, also put the Hugging Face checkpoint inside as the source of the tokenizer.