Pruning Object Detection Models with TensorFlow

At the moment there is no official model pruning support for TensorFlow's 1.x Object Detection API. This repo attempts to solve this issue. A base example is setup for the InceptionV2-based FasterRCNN models.

This repo contains the full code for the blog post: Pruning Mask RCNN Models with TensorFlow

Setup

Clone repo with submodules

git clone --recurse-submodules git@github.com:panchgonzalez/tf_object_detection_pruning.git
cd tf_object_detection_pruning

Apply patch to tensorflow.contrib.model_pruning library and compile

cd tensorflow

# Apply patch
git apply -v ../tf_model_pruning.patch

# Compile
bazel build tensorflow/contrib/model_pruning:strip_pruning_vars

Apply patch to models.research.object_detection and models.research.slim libraries that will allow us to prune InceptionV2 based MaskRCNN models

cd models

# Apply patch
git apply -v ../object_detection_pruning.patch

# Compile object detection protobufs
pushd research
protoc object_detection/protos/*.proto --python_out=.

# Install object detection
pip install .
popd

# Install slim
pushd research/slim
pip install .
popd

# Compiling and installing cocoapi
cd ../cocoapi
python setup.py build_ext --inplace
make
python setup.py install
cp -r pycocotools ../models/research

Train with Model Pruning

To train with model pruning turned on pass the following flags to model_main.py

• --sparsity: target sparsity level
• --pruning_start_step: start pruning at this training step
• --pruning_start_step: stop pruning at this training step

python ${OBJECT_DETECTION_PATH}/object_detection/model_main.py \
    --pipeline_config_path=${PIPELINE_CONFIG_PATH} \
    --model_dir=${MODEL_DIR} \
    --sample_1_of_n_eval_examples=$SAMPLE_1_OF_N_EVAL_EXAMPLES \
    --alsologtostderrcd ../ \
    --throttle_secs=2100 \
    --sparsity=0.85 \
    --pruning_start_step=100000 \
    --pruning_end_step=200000

During training you can check the overall sparsity in tensorboard

Known issues:

It seems that training with TF 1.15 returns the following runtime error

RuntimeError: Init operations did not make model ready for local_init. Init op: group_deps, init fn: None, error: Variables not initialized: model_pruning/last_mask_update_step

This is fixed by downgrading to TF 1.14. Thanks to @anshkumar for pointing this out.

References

Michael Zhu and Suyog Gupta, “To prune, or not to prune: exploring the efficacy of pruning for model compression”, 2017 NIPS Workshop on Machine Learning of Phones and other Consumer Devices (https://arxiv.org/pdf/1710.01878.pdf)