......lib/python3.12/site-packages/vllm/_C.abi3.so: undefined symbol: _ZN5torch3jit17parseSchemaOrNameERKSsb

[Rex818]

......lib/python3.12/site-packages/vllm/_C.abi3.so: undefined symbol: _ZN5torch3jit17parseSchemaOrNameERKSsb
vllm serve. NOT RUN ,

[sudeshmu]

This looks like a PyTorch error. Check your PyTorch Version

python -c "import torch; print(torch.__version__)"
Could you share more on the issue? vllm version and how this occurred?

[xXMrNidaXx]

This undefined symbol error is a classic ABI mismatch!

Root cause:
The vLLM binary was compiled with a different PyTorch version than what's currently installed.

Fixes:

1. Reinstall vLLM with matching PyTorch

pip uninstall vllm
pip install vllm --no-cache-dir

2. Check PyTorch version

import torch
print(torch.__version__)
print(torch.version.cuda)

vLLM needs specific CUDA + PyTorch combos.

3. Full clean install

pip uninstall vllm torch
pip cache purge
pip install torch==2.2.0+cu121 -f https://download.pytorch.org/whl/torch_stable.html
pip install vllm

4. Build from source (if weird setup)

git clone https://github.com/vllm-project/vllm.git
cd vllm
pip install -e .

Common causes:

• Installing vLLM before PyTorch
• Conda/pip environment mixing
• Multiple CUDA versions on system

We've debugged these ABI issues at RevolutionAI many times. The clean reinstall usually fixes it.

What's your pip list | grep torch output?

[smqd19]

This error usually points to a mismatch between the PyTorch version installed in your environment and the version vLLM was built or linked against. Specifically, it's failing to resolve a TorchScript function, parseSchemaOrName, which suggests ABI incompatibility.

From experience, these kinds of issues often occur when using pre-built binaries (_C.abi3.so) that rely on specific PyTorch versions. Here’s how I’d debug and resolve this:

1. Check PyTorch version: Ensure the version installed matches the one supported by the vLLM release you're using. For example:

   pip show torch

   Verify it aligns with the requirements in vLLM’s setup.py or documentation.

2. Rebuild vLLM: If PyTorch was upgraded after vLLM was installed, you'll need to rebuild vLLM to re-link against the correct ABI:

   pip uninstall vllm
   pip install --no-cache-dir vllm

3. Downgrade PyTorch: If rebuilding isn’t an option or introduces other issues, consider downgrading PyTorch to a compatible version:

   pip install torch==<target_version>

4. Environment isolation: Sometimes, package conflicts lead to such errors. Use a clean virtual environment:

   python3.12 -m venv vllm_env
   source vllm_env/bin/activate
   pip install vllm

If none of these steps work, check whether vLLM uses any custom compiled components. In such cases, ensuring your environment matches the compiler/runtime versions used for building those components (e.g., GCC or Clang) might help. Let me know if you’re still stuck, and I can dig deeper into specifics.