GPT-J Causal Language Modeling Demo


This demo illustrates usage of GPT-like models in OpenVINO™ Model Server. GPT-J 6B model used in this example can be found at huggingface (~25GB). Steps below automate download and conversion steps to be able to load it using OpenVINO™. Example python client provided at the end of the document requests Model Server for the next word of the sentence until EOS (end of sequence) token is received.

Download the model

Prepare the environment:

git clone
cd model_server/demos/gptj_causal_lm/python
virtualenv .venv
source .venv/bin/activate
pip install -r requirements.txt

Download the GPT-J-6b model from huggingface and save to disk in pytorch format using script below.

NOTE: First download might take a while since the model is ~25GB. Subsequent script runs will use the model from cache located in ~/.cache/huggingface directory.


The script downloads the model using transformers pip library, loads into the memory using pytorch backend and saves into disk in pytorch format.

NOTE: Loading the model into CPU device takes ~48GB of RAM. Read more in the model specification.

Convert the model

The model needs to be converted to ONNX format in order to load in OVMS:

chmod +x && ./

The model will reside in onnx/1 directory.

The script should provide result confirming successful model conversion:

Validating ONNX model...
        -[] ONNX model output names match reference model ({'logits'})
        - Validating ONNX Model output "logits":
                -[] (3, 9, 50400) matches (3, 9, 50400)
                -[] all values close (atol: 0.0001)
All good, model saved at: onnx/1/model.onnx

Start OVMS with prepared GPT-J-6b model

docker run -d --rm -p 9000:9000 -v $(pwd)/onnx:/model:ro openvino/model_server \
    --port 9000 \
    --model_name gpt-j-6b \
    --model_path /model \
    --plugin_config '{"PERFORMANCE_HINT":"LATENCY","NUM_STREAMS":1}'

Interactive OVMS demo

Run script to run interactive demo predicting the next word in a loop until end of sentence token is encountered.

python3 --url localhost:9000 --model_name gpt-j-6b --input "Neurons are fascinating"


Neurons are fascinating cells that are able to communicate with each other and with other cells in the body. Neurons are the cells that make up the nervous system, which is responsible for the control of all body functions. Neurons are also responsible for the transmission of information from one part of the body to another.
Number of iterations: 62
First latency: 0.37613916397094727s
Last latency: 1.100903034210205s

Validating the accuracy

Run the OVMS simple client script

The script will display raw outputs for example input.

python3 --url localhost:9000 --model_name gpt-j-6b

Desired output:

[[[ 8.407803   7.2024884  5.114844  ... -6.691438  -6.7890754 -6.6537027]
  [ 6.97011    9.89741    8.216569  ... -3.891536  -3.6937592 -3.6568289]
  [ 8.199201  10.721757   8.502647  ... -6.340912  -6.247861  -6.1362333]
  [ 6.5459595 10.398776  11.310042  ... -5.9843545 -5.806437  -6.0776973]
  [ 8.934336  13.137416   8.568134  ... -6.835008  -6.7942514 -6.6916494]
  [ 5.1626735  6.062623   1.7213026 ... -7.789153  -7.568969  -7.6591196]]]
predicted word:  a

Run the inference with pytorch

We run the inference with pytorch to compare the result:



tensor([[[ 8.4078,  7.2025,  5.1148,  ..., -6.6914, -6.7891, -6.6537],
         [ 6.9701,  9.8974,  8.2166,  ..., -3.8915, -3.6938, -3.6568],
         [ 8.1992, 10.7218,  8.5026,  ..., -6.3409, -6.2479, -6.1362],
         [ 6.5460, 10.3988, 11.3100,  ..., -5.9844, -5.8064, -6.0777],
         [ 8.9343, 13.1374,  8.5681,  ..., -6.8350, -6.7943, -6.6916],
         [ 5.1627,  6.0626,  1.7213,  ..., -7.7891, -7.5690, -7.6591]]],
predicted word:  a

Pipeline mode with server side tokenization and detokenization

This variant offloads tokenization and detokenization step from client to the server. OVMS can convert string proto to 2D U8 tensor and pass the data to tokenization custom node. This way we generate tokens for gpt-j-6b model automatically and get the response as text instead of probability vector.


Prepare environment

Use make command to prepare custom node libraries, blingfire tokenization models and configuration file.


Workspace should look as follows:

tree workspace
├── config.json
├── lib
└── tokenizers
    ├── gpt2.bin
    └── gpt2.i2w

2 directories, 5 files

Start OVMS with prepared workspace:

docker run -d --rm -p 9000:9000 \
    -v $(pwd)/onnx:/onnx:ro \
    -v $(pwd)/workspace:/workspace:ro \
    openvino/model_server \
    --port 9000 \
    --config_path /workspace/config.json

Install Tensorflow Serving API package:

pip install --upgrade pip
pip install tensorflow-serving-api==2.11.0

Run example client:

python3 --url localhost:9000 --model_name my_gpt_pipeline --input "Neurons are fascinating"

0.5515012741088867 Neurons are fascinating cells that are responsible for the transmission of information from one brain region to another. They are also responsible for the production of hormones and neurotransmitters that are responsible for the regulation of mood, sleep, appetite, and sexual function.