AFAIK:
Hi, when I wanted to compile Pytorch I checked for this flag. AFAIK it enables your Pytorch to use NVIDIA TensorRT library.
Hopefully, any source building works even with e.g. 3.5 capability value in TORCH_ARCH with USE_TENSORRT set.
Quoting TensorRT site:
“You can import trained models from every deep learning framework into TensorRT. After applying optimizations, TensorRT selects platform specific kernels to maximize performance on Tesla GPUs in the data center, Jetson embedded platforms, and NVIDIA DRIVE autonomous driving platforms.
With TensorRT developers can focus on creating novel AI-powered applications rather than performance tuning for inference deployment.”
CCMake Hint:

Supported HW (Cuda Capability > 5):

  
      docs.nvidia.com
  
  
    

Support Matrix :: NVIDIA Deep Learning TensorRT Documentation 2