Training a model with TensorFlow 1.x creates a folder containing a GraphDef file (usually ending with a .pb or .pbtxt extension) and a set of checkpoint files. What you need for mobile or embedded deployment is a single GraphDef file that has been “frozen,” or had its variables converted into inline constants, so everything is in one file. To handle the conversion, TensorFlow provides freeze_graph.py, which is automatically installed with the vai_q_tensorflow quantizer.
An example of command-line usage is as follows:
$ freeze_graph \ --input_graph /tmp/inception_v1_inf_graph.pb \ --input_checkpoint /tmp/checkpoints/model.ckpt-1000 \ --input_binary true \ --output_graph /tmp/frozen_graph.pb \ --output_node_names InceptionV1/Predictions/Reshape_1
–input_graph should be an inference
graph other than the training graph. Because the operations of data preprocessing and
loss functions are not needed for inference and deployment, the frozen_graph.pb should only include the main part of the
model. In particular, the data preprocessing operations should be taken in the
Input_fn to generate correct input data for quantize
tf.layers.batch_normalization. For models using
tf.keras.backend.set_learning_phase(0)before building the graph.
freeze_graph --helpfor more options.
The input and output node names vary depending on the model, but you can inspect and estimate them with the vai_q_tensorflow quantizer. See the following code snippet for an example:
$ vai_q_tensorflow inspect --input_frozen_graph=/tmp/inception_v1_inf_graph.pb
The estimated input and output nodes cannot be used for quantization if the graph has in-graph pre- and post-processing. This is because some operations are not quantizable and can cause errors when compiled by the Vitis AI compiler, if you deploy the quantized model to the DPU.
Another way to get the input and output name of the graph is by visualizing the graph. Both TensorBoard and Netron can do this. See the following example, which uses Netron:
$ pip install netron $ netron /tmp/inception_v3_inf_graph.pb