Unexpected dependency requirements from `MultiScaleDeformableAttention.so` when `ninja` is installed but CUDA devel files are not installed.

[cainmagi]

Short explanation

The subpackage MultiScaleDeformableAttention.so in this project causes an unexpected behavior in transformers.DeformableDetrModel. The behavior can be summarized by:

1. If ninja is not installed, nothing wrong will happen.
2. If CUDA toolkits and the devel files are installed locally, no matter whether ninja is installed or not, nothing wrong will happen.
3. If CUDA devel files are not installed and we only use the PyPI to install the CUDA run time, in this case, every time when accessing transformers.DeformableDetrModel, two error messages will show:

   Could not load the custom kernel for multi-scale deformable attention: CUDA_HOME environment variable is not set. Please set it to your CUDA install root.
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/pyxxx_cuxxx/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory

   Note that the above messages will NOT show as long as we do not install ninja. It seems that these messages will not actually influence the processing of transformers.DeformableDetrModel. The model is still able to produce outputs with these messages exist.

Background

Now, many deep learning frameworks will automatically install their own CUDA runtime when using pip wheels. For example,

python -m pip install torch

Running the above command on Linux (1) with GPU (drivers) available and (2) with CUDA not installed, the installation will contain CUDA run time libraries.

However, such an installation will not install the developed files (including the headers and some shared files). In this case, torch.cuda.is_avaiable() returns True, but the CUDA_HOME environment variable is not available.

For a strange reason, this pacakge MultiScaleDeformableAttention.so will require the environment variable CUDA_HOME if and only if ninja is installed. This behavior can be inspected when using transformers package.

Reproduce the error

1. Start a new docker container by

   docker run --gpus all -it --rm --shm-size=1g python:3.10-slim bash

2. Install dependencies

   pip install transformers[torch] requests pillow timm

3. Run the following script (copied from the document), it works fine and does not show any message.

   from transformers import AutoImageProcessor, DeformableDetrModel
   from PIL import Image
   import requests
   
   url = "http://images.cocodataset.org/val2017/000000039769.jpg"
   image = Image.open(requests.get(url, stream=True).raw)
   
   image_processor = AutoImageProcessor.from_pretrained("SenseTime/deformable-detr")
   model = DeformableDetrModel.from_pretrained("SenseTime/deformable-detr")
   
   inputs = image_processor(images=image, return_tensors="pt")
   
   outputs = model(**inputs)
   
   last_hidden_states = outputs.last_hidden_state
   list(last_hidden_states.shape)

4. Install ninja:

   pip install ninja

5. Run the same script again, this time, the following warning messages will show

       
                                  !! WARNING !!
   
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   Your compiler (c++) is not compatible with the compiler Pytorch was
   built with for this platform, which is g++ on linux. Please
   use g++ to to compile your extension. Alternatively, you may
   compile PyTorch from source using c++, and then you can also use
   c++ to compile your extension.
   
   See https://github.com/pytorch/pytorch/blob/master/CONTRIBUTING.md for help
   with compiling PyTorch from source.
   !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
   
                                 !! WARNING !!
   
     warnings.warn(WRONG_COMPILER_WARNING.format(
   Could not load the custom kernel for multi-scale deformable attention: CUDA_HOME environment variable is not set. Please set it to your CUDA install root.
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   Could not load the custom kernel for multi-scale deformable attention: /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/MultiScaleDeformableAttention.so: cannot open shared object file: No such file or directory
   

   Certainly, /root/.cache/torch_extensions/py310_cu124/MultiScaleDeformableAttention/ is empty.

This issue was initially proposed in transformers repository. The maintainer of transformers suggest that I should submit the issue here.

The related issues are:

• A warning message showing that MultiScaleDeformableAttention.so is not found in /root/.cache/torch_extensions if ninja is installed with transformers huggingface/transformers#35349
• https://app.semanticdiff.com/gh/huggingface/transformers/pull/32834/overview

Personally, I think it is not reasonable that the dynamic library MultiScaleDeformableAttention would ask for the devel files in the run time. By the way, this behavior only exists when the ninja is installed. Therefore, I am suspecting whether there should be a check for blocking the behaviors related to ninja in the run time.

Further materials

I have tried to use some Docker images with CUDA preinstalled. The tested images are:

• nvcr.io/nvidia/pytorch:24.12-py3 (Ubuntu 24.04)
• cainmagi/deformable-detr (Debian 12)

In both images, we have CUDA toolkits and the devel files preinstalled. In this case,

1. MultiScaleDeformableAttention can be built successfully
2. transformers will not complain for MultiScaleDeformableAttention.so even if we do not built MultiScaleDeformableAttention and copy it to /root/.cache/torch_extensions/.