How does TensorRT set the number of bindings (NbBindings) for the engine


I have been working with a GoogleNet model from torchvision and I have converted it to a trt engine using . I have converted the model to an engine file, which I read into C++. I have been able to infer correct results in the python API with torch2trt and tensorrt. I have been trying to understand how inference works and it seems buffers are allocated according to the bindings before inferring on them. Ideally, there should be an input and an output buffer or more in most cases. In my case, I only see an output buffer and hence the engine->getNbBindings as 1. It’s the same value while using the python API. My question is how does TensorRT set the number of bindings? And in my case, did I call the torch2trt in a wrong way? If so, what is the correct way? Can I still work with 1 binding in the C++ API. I have attached files below for better understanding.


TensorRT Version: 5.1.5
GPU Type: GeForce RTX 2080
Nvidia Driver Version: 440
CUDA Version: 10.0
CUDNN Version: 7.6.5
Operating System + Version: Ubuntu 18.04
Python Version (if applicable): Python 3.6.9
TensorFlow Version (if applicable):
PyTorch Version (if applicable):
Baremetal or Container (if container which image + tag): 1.4.0

Relevant Files - converts the checkpoint to a serialized engine file.
checkpoint/ - Original PyTorch checkpoint
checkpoint/trt.engine - The trt file that was already converted. ( converts another one)
include/torch2trt.h - header file
src/torch2trt.cpp - source file

Steps To Reproduce

  1. tar -xvf googlenet.tar.gz
  2. Run scripts/ by ensuring you have the libraries installed
  3. Create build directory
  4. cd build
  5. cmake … && make -j8
  6. ./googlenet_node

Edit: I just realized I cannot upload a tar file. Hence, sharing a Google Drive link

Directory Structure:
Parent Directory: GoogleNet
------ include
------ ------ torch2trt.h
------ build
------ src
------ ------ torch2trt.cpp
------ scripts
------ ------ convert_to_trt.oy
------ checpoint
------ ------
------ ------ trt.engine

You need to pass the current input/output name to the script to generate the binding.


Thanks a lot for the prompt response SunilJB!
I will try it out and revert with my findings.

Hey SunilJB,
I tried it out. It seems “input.1” is the input_name and “318” is the output tensor but even after converting the model to TensorRT, I find that the number of bindings are 1.


Can you try generating your model using torch2onnx and ONNX parser workflow?
Please refer below link:

You can also use trtexec command line tool for debugging and converting the ONNX model.