utensor_cgen: C/C++ code generator for uTensor

Version: vremove-legacy.dev6ba0fac+dirty

Documentation update: Dec 16, 2020

Read Source Code on GitHub

Full API Documentation

Installation (Python 2 & 3)

For Users

  • with setup.py

$ python setup.py install
$ pip install utensor_cgen

For Developers

# install `utensor_cgen` (develop mode)
$ PIPENV_VENV_IN_PROJECT=1 pipenv install -d

# spawn a subshell and activate virtualenv
$ pipenv shell

# get help message of `utensor-cli`
$ utensor-cli -h

Troubleshooting with pipenv

  • If you have troubles with installation using pipenv, try

    $ PIPENV_VENV_IN_PROJECT=1 pipenv install -d --skip-lock
  • there is known issue of pip and pipenv, plz refer to this issue for detail

    • short answer: downgrade to pip==18.0 may help :)

  • Tensorflow requires setuptools<=39.1.0 (the latest is 40.4.3 by the time this README is writen)

    • plz downgrade to setuptools==39.1.0

    • my recommendation is to use virtualenv

Overall Architecture


Basic Usage

Model File Inspection

$ utensor-cli show <model.pb>

Show all nodes and detailed information of given pb file or a uTensorGraph pickle file

Run utensor-cli show --help for detailed information.

Convert Model File to C/C++ Code

IMPORTANT: pb file is deprecated in favor of Tensorflow 2.x, please refer to End-to-End Training with Keras for detail

$ utensor-cli convert <model.pb> \
  --output-nodes=<node name>[,<node name>,...] \

Convert given pb file into cpp/hpp files.

Note that --output-nodes is required options. It’s the names of nodes you want to output, seperated by comma for multiple values.

In graph theory terminology, they are leaf nodes of your graph.

Use --config to pass a configuration file to the cli, you can use generate-config command to generate one (see below).


$ utensor-cli convert simple_model.pb --output-nodes=pred,logits

Run utensor-cli convert --help for detailed information.


utensor-cli use toml as configuration format.

You can generate configuration file of given target as following:

$ utensor-cli generate-config --target <target name> [-o filename.toml]

This command will generate a toml file listing all configurable values with its defaults.

You can modify the value and pass the file to cli with --config flag.


# generate config file
$ utensor-cli generate-config --target utensor -o myconfig.toml

# after editting myconfig.toml
$ utensor-cli convert mymodel.pb --config=myconfig.toml --output-nodes=output,...

Use utensor_cgen as Library

Subgraph Isomorphic Matcher

With uTensorGraphMatcher, performing isomorphic subgraph matching along with replacing or manipulating the matched subgraph(s) takes just a few line of code:

from utensor_cgen.matcher import uTensorGraphMatcher

# `pattrn_ugraph` is the pattern to match with
pattrn_ugraph = ...
matcher = uTensorGraphMatcher(pattrn_ugraph)

# a larget graph to perform subgraph match
subject_ugraph = ...

# matches is a list of `uTensorGraphMatch` objects
matches = matcher.match_all(subject_ugraph)
if matches:
  # do stuff with the matches

Use Case: Node Fusion

Note: we’ll use operation/node/layer interchangeably in the documentation

  • It’s commonly seen pattern in convolution neural network (CNN), conv -> relu -> pooling. That is, a 2D convolution followed by a relu layer and then a pooling down sampling layer.

  • With our uTensorGraphMatcher, you can locate such pattern in your CNN model and fuse/replace matched nodes into one optimized QuantizedFusedConv2DMaxpool node.

  • Left: original graph

  • Middle: matched convolution layer

  • Right: replace the matched layer with specialized QuantizedFusedConv2DMaxpool node


Use Case: Dropout Layer Removal

  • Though dropout is an effective technique to improve training performance of your model, it’s not necessary during inference phrase.

  • In the mainstream frameworks such as Tensorflow or PyTorch, an dropout layer is typically implemented with other elementary operations/nodes. As a result, finding and removing those nodes for inference optimization (both in model size and prediciton time) is not trivial and error prone.

  • With our uTensorGraphMatcher, you can find and remove the dropout nodes as illustrated in the following picture.

    • Left: original graph with dropout Layers

    • Middle: matched dropout layers

    • Right: graph with dropout layers removed


We use mainly Tensorflow for declaring the pattern graph for matcher now.

High-level graph builder is on its way, see Future Works for detail.

Offline Tensor Memory Allocation

Considering following simple multi layers perceptron (simple_mnist.pb):


Once enabled the optimization transformer, tensor_alloc, an offline tensor memory allocation planner, utensor-cli will generate uTensor runtime codes that use following optimized allocation plan:


  • y-axis: tensor names ordered by topological sorting

  • x-axis: these are the memory span occupied by each tensor, that is, the memory address offset and

the size of the tensor

How to Serve Your Model on uTenosr


  1. Freeze your tensorflow.Graph

  1. Follow instructions in Installation (Python 2 & 3) section to install utensor_cgen

  • then utensor-cli should be available in your console

  1. Inspect your pb file to find the output node

# verbose mode
$ utensor-cli show graph.pb

# or oneline mode
$ utensor-cli show graph.pb --oneline
  1. convert the protobuf file to C/C++ source code with utensor-cli

  • supose the output node is pred in graph.pb

$ utensor-cli convert --output-nodes=pred graph.pb
  1. Compile your application code with generated C/C++ and weights files

  • You should find your model C/C++ and weights files in directories models and constants respectively



  1. follow the steps in For Developers section

  2. run tests as following

# run with `make`
$ make tests

# run with `pipenv`
$ pipenv run pytest -m 'not slow_test and not deprecated' tests

Future Works

  1. High-level graph builder api for building uTensorGraph.

    • Currently utensor_cgen uses TensorFlow api for building IR graph, uTensorGraph.

    • With high-level graph builder, users can build their uTensorGraph easily and do not need to take care of the integrity of the graph. The builder will take care of it automatically.

  1. Automaic-Update TFLite fbs file