TensorRT Conversion

PyTorch -> ONNX -> TensorRT

This repo includes installation guide for TensorRT, how to convert PyTorch models to ONNX format and run inference with TensoRT Python API.

The following table compares the speed gain got from using TensorRT running YOLOv5.

Device/ Env	PyTorch (FP16)	TensorRT (FP16)
RTX 2060	60-61	96-97
Jetson Xavier	17-18	38-39

Notes: YOLO model in comparison is using YOLOv5-L with image size of 352x416. Units are in FPS.

Example conversion of YOLOv5 PyTorch Model to TensorRT is described in examples folder.

Installation

Recommended CUDA version is

• cuda-10.2 + cuDNN-7.6

Tested environments:

• CUDA 10.2 + cuDNN 7.6
• TensorRT 7.0.0.11
• ONNX 1.7
• ONNXRuntime 1.3
• Protobuf >= 3.12.3
• CMake 3.15.2/ CMake 3.17.3
• PyTorch 1.5 + CUDA 10.2

Protobuf

Only Protobuf version >= 3.12.3 is supported in ONNX_TENSORRT package. So, you need to build the latest version from source.

To build protobuf from source, the following tools are needed:

sudo apt install autoconf automake libtool curl make g++ unzip

Clone protobuf repository and make sure to also clone submodules and generated the configure script.

git clone --recursive https://github.com/protocolbuffers/protobuf.git
cd protobuf
./autogen.sh
./configure --prefix=/usr
make -j$(nproc)
sudo make install 
sudo ldconfig # refresh shared library cache

Verify the installation:

protoc --version

You should see the installed libprotoc version.

NVIDIA Driver

First detect your graphics card model and recommended driver.

ubuntu-drivers devices

If you don't find your desired driver version, you can enable Nvidia beta driver repository.

sudo add-apt-repository ppa:graphics-drivers/ppa

Then install the desired driver version using:

sudo apt install nvidia-driver-440
sudo reboot

CUDA

Go to CUDA toolkit archive and download your desired CUDA version and installation method.

Below is the sample installation method for CUDA 10.2 deb file.

wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-ubuntu1804.pin
sudo mv cuda-ubuntu1804.pin /etc/apt/preferences.d/cuda-repository-pin-600
wget http://developer.download.nvidia.com/compute/cuda/10.2/Prod/local_installers/cuda-repo-ubuntu1804-10-2-local-10.2.89-440.33.01_1.0-1_amd64.deb
sudo dpkg -i cuda-repo-ubuntu1804-10-2-local-10.2.89-440.33.01_1.0-1_amd64.deb
sudo apt-key add /var/cuda-repo-10-2-local-10.2.89-440.33.01/7fa2af80.pub
sudo apt-get update
sudo apt-get -y install cuda

Check using:

nvcc -V

cuDNN

Go to NVIDIA cuDNN and download your desired cuDNN version.

You need to download cuDNN Runtime Library and Developer Library. Code Samples and User Guide is not essential.

Then install step by step:

sudo dpkg -i libcudnn8_x.x.x-1+cudax.x_amd64.deb
sudo dpkg -i libcudnn8-dev_8.x.x.x-1+cudax.x_amd64.deb

TensorRT

Download TensorRT from the following link:

https://developer.nvidia.com/tensorrt

Be careful to download to match with your CUDA install method. For example, if you installed CUDA with deb file, download TensorRT deb file also. Otherwise, it won't work.

The following example will install TensorRT deb file method. For other version of TensoRT installation, please check official documentation.

os="ubuntu1x04"
tag="cudax.x-trt7.x.x.x-ga-yyyymmdd"
sudo dpkg -i nv-tensorrt-repo-${os}-${tag}_1-1_amd64.deb

sudo apt-key add /var/nv-tensorrt-repo-${tag}/7fa2af80.pub

sudo apt-get update
sudo apt-get install tensorrt cuda-nvrtc-x-y

Where x-y for cuda-nvrtc is 10-2 or 11-0 depending on your CUD version.

If you plan to use TensorRT with TensorFlow, install this:

sudo apt install uff-converter-tf

Verify the installation with

dpkg -l | grep TensorRT

You should see libnvinfer, tensorrt and other related packages installed.

PyCUDA

PyCUDA is used within Python wrappers to access NVIDIA’s CUDA APIs.

Install PyCUDA with the following command:

pip3 install pycuda

If you faced this error: command 'aarch64-linux-gnu-gcc' failed with exit status 1, install like this: pip3 install pycuda --user.

If you cannot access cuda driver with PyCUDA, please uninstall PyCUDA, clean pip cache and install PyCUDA again.

pip3 cache purge

To use the above command pip3 cache purge, you need to have pip version >= 20.x.x.

CMake

CMake >= 3.13 is required but on Ubuntu 18.04, installed version is 3.10.2. So, upgrade CMake.

Download latest CMake from here.

Install OpenSSL:

sudo apt install libssl-dev

Then, install:

tar -xvzf cmake-3.x.x.tar.gz
cd cmake-3.x.x
./bootstrap
make -j$(nproc)
sudo make install

Verify the installation:

cmake --version

ONNX_TensorRT

Parses ONNX models for execution with TensorRT.

Install Pre-requisities:

sudo apt install swig

Install ONNX_TRT:

git clone https://github.com/onnx/onnx-tensorrt
cd onnx-tensorrt
git submodule update --init --recursive
mkdir -p build && cd build
cmake .. -DTENSORRT_ROOT=/usr/src/tensorrt
make -j$(nproc)
sudo make install
cd ..
sudo python3 setup.py build
sudo python3 setup.py install

Possible errors when running setup.py:

• error: command 'swig' failed with exit status 1. To fix this, do the following: Add #define TENSORRTAPI at the top of NvOnnxParser.h.
• error: command 'aarch64-linux-gnu-gcc' failed with exit status 1. This error will be occurred on Jetson platforms. To fix: Delete '-m64,' line in setup.py and try to re-build.

trtexec

A command line wrapper tool to serve two main purposes: benchmarking networks on random data and generating serialized engines from models.

trtexec can build engines from models in Caffe, UFF (TensorFlow), or ONNX format.

trtexec is included when you installed TensorRT but not enabled. You need to build to use it.

Switch to this trtexec directory and build it:

cd /usr/src/tensorrt/samples/trtexec/
sudo make

Then, the binary named trtexec will be created in <TensorRT root directory>/bin. Add this path in .bashrc.

gedit ~/.bashrc

export PATH=$PATH:/usr/src/tensorrt/bin

source ~/.bashrc

ONNX

pip3 install onnx

ONNXRuntime

CPU:

pip3 install onnxruntime

GPU

pip3 install onnxruntime-gpu

ONNX Simplifier

pip3 install onnx-simplifier

Conversion

PyTorch to ONNX

Run onnx_export.py.

Detail steps are as follows:

Load the PyTorch Model.

device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
model = Model()
model.load_state_dict(torch.load(model_path, map_location=device))
model.to(device).eval()

Prepare the input:

img = torch.zeros((1, 3, height, width)).to(device)

Note that height and width is fixed. Dynamic input shape is still not available in PyTorch >> ONNX >> TensorRT.

Export to ONNX format:

torch.onnx.export(
    model,                  # PyTorch Model
    img,                    # Input tensor
    f,                      # Output file (eg. 'output_model.onnx')
    opset_version=12,       # Operator support version
    input_names=['image']   # Input tensor name (arbitary)
    output_names=['output'] # Output tensor name (arbitary)
)

opset_version is very important. Some PyTorch operators are still not supported in ONNX even if opset_version=12. Default opset_version in PyTorch is 12. Please check official ONNX repo for supported PyTorch operators. If your model includes unsupported operators, convert to supported operators. For example, torch.repeat_interleave() is not supported, it can be converted into supported torch.repeat() + torch.view() to achieve the same function.

ONNX Simplifier

onnxsim will be used to simplify the exported ONNX model. This onnxsim will strip some unnecessary operations and will reduce the number of layers. Moreover, it will get rid of unsupported operators when converting to TensorRT.

An example before and after simplification from official repo is shown below:

It includues optimizers from onnx.optimizer, eliminate constant nodes and can run with 3 versions:

Web Version

Open official published https://convertmodel.com page and choose ONNX as the output format and convert it.

Commandline Version

If the web version won't work well, run the following command to simplify the ONNX model:

python3 -m onnxsim <input_onnx_model> <output_onnx_model>

For more available functions this command can do like skipping optimization and others:

python3 -m onnxsim -h

Python In-Script Version

import onnx
from onnxsim import simplify

onnx_model = onnx.load(f)
simplified_model, check = simplify(onnx_model)

assert check, "Simplified ONNX model could not be validated."

onnx.save(simplified_model, 'onnx_model_simplified.onnx')

After all, check the exported ONNX model:

onnx.checker.check_model(simplified_model)
print(onnx.helper.printable_graph(simplified_model.graph))  # print a human readable representation of the graph

You can view the ONNX model with this tool Netron.

Note: Don't convert PyTorch to ONNX on Jetson; it will take more GPU memory usage. Try to do this on host PC. Sometimes, commandline method won't work, so recommended method is In-script version.

ONNX to TensorRT with onnx-tensorrt

ONNX-TensorRT package installed above will be used to convert the ONNX model (.onnx) to Tensort model (.trt).

You can also run .onnx model directly with TensorRT Python API but converting to .trt will be more convenient.

To convert, run the following command in your terminal:

onnx2trt model.onnx -o model.trt -b 1 -d 16

• -o: To output TensorRT engine file
• -b: Set batch size (default: 32)
• -d: Set Model data type (16 for FP16, 32 for FP32)

Please see other available options and their usage on official repo.

Note: Converted TRT model on one device will not result the same output on other device. This is more obvious if you use other optimization passes option. Try to run this on each device.

ONNX to TensorRT with trtexec

trtexec commandline tool can be used to convert the ONNX model instead of onnx2trt.

To convert ONNX model, run the following:

trtexec --onnx=model.onnx --saveEngine=model.trt --workspace=1024 --fp16

It also includes model benchmarking and profiling. To see other available options and use cases, check out official Documentation.

Run TRT Model

First implement a logging interface through which TensorRT reports errors, warnings and informational messages.

import tensorrt as trt

TRT_LOGGER = trt.Logger(trt.Logger.WARNING)

Then, read the TRT model and deserialize it.

with open('trt_model.trt', 'rb) as f, trt.Runtime(TRT_LOGGER) as runtime:
    engine = runtime.deserialize_cuda_engine(f.read())

Allocate some host and device buffers for inputs and outputs.

import pycuda.driver as cuda
import pycuda.autoinit

h_input = cuda.pagelocked_empty(trt.volume(engine.get_binding_shape(0)), dtype=np.float32)
h_output = cuda.pagelocked_empty(trt.volume(engine.get_binding_shape(1)), dtype=np.float32)
# Allocate device memory for inputs and outputs.
d_input = cuda.mem_alloc(h_input.nbytes)
d_output = cuda.mem_alloc(h_output.nbytes)
# Create a stream in which to copy inputs/outputs and run inference.
stream = cuda.Stream()

Finally, run inference with created engine:

with engine.create_execution_context() as context:
    # Transfer input data to the GPU.
    cuda.memcpy_htod_async(d_input, h_input, stream)
    # Run inference.
    context.execute_async(bindings=[int(d_input), int(d_output)], stream_handle=stream.handle)
    # Transfer predictions back from the GPU.
    cuda.memcpy_dtoh_async(h_output, d_output, stream)
    # Synchronize the stream
    stream.synchronize()
    # Return the host output. 
    return h_output

There is also an option to run ONNX model directly with TensorRT Python API, but it is not recommended.

Examples

Example conversion of YOLOv5 model into TRT model can be seen in conversion.

You can see the example converted models in examples.

References

• YOLOv5
• TensorRT Documentation
• ONNX
• ONNX-Runtime
• ONNX-TensorRT
• ONNX Simplifier
• trtexec