UV CUDA Setup

Configure uv-managed Python projects to use CUDA-enabled PyTorch instead of CPU-only version.

When to Use

• •User reports CUDA available: False in PyTorch
• •Setting up new ML/AI project with GPU requirements
• •Migrating pip-based project to uv with CUDA dependencies
• •User asks about GPU acceleration in Python projects

Problem

By default, uv add torch installs the CPU-only version from PyPI. This is because:

1. •PyPI hosts CPU-only torch wheels
2. •CUDA wheels are on a separate PyTorch index
3. •uv respects the lock file which pins CPU version

Solution

Step 1: Check Current State

import torch
print(f"PyTorch: {torch.__version__}")
print(f"CUDA available: {torch.cuda.is_available()}")
print(f"CUDA version: {torch.version.cuda}")

If output shows CUDA available: False, proceed with fix.

Step 2: Identify CUDA Version

# Check NVIDIA driver
nvidia-smi

# Check CUDA toolkit
echo $env:CUDA_PATH

Match CUDA version to PyTorch index:

• •CUDA 11.8 → cu118
• •CUDA 12.1 → cu121
• •CUDA 12.4 → cu124
• •CUDA 12.6 → cu126
• •CUDA 13.0 → cu130

Step 3: Configure pyproject.toml

Add the following to pyproject.toml:

[project]
dependencies = [
    "torch>=2.0",
    # other dependencies...
]

# Define PyTorch CUDA index
[[tool.uv.index]]
name = "pytorch-cu126"  # adjust version as needed
url = "https://download.pytorch.org/whl/cu126"
explicit = true

# Source torch from CUDA index
[tool.uv.sources]
torch = { index = "pytorch-cu126" }

Step 4: Reinstall Dependencies

# Delete existing lock file
Remove-Item uv.lock -Force

# Sync dependencies (will fetch CUDA torch)
uv sync

Step 5: Verify

uv run python -c "import torch; print('CUDA:', torch.cuda.is_available())"

Expected output: CUDA: True

Common Issues

Lock File Conflict

If uv run reinstalls CPU version:

• •The lock file takes precedence
• •Always delete uv.lock after changing indexes

Wrong CUDA Version

If PyTorch fails to load:

• •Check CUDA toolkit version matches index
• •Use nvidia-smi to see driver CUDA version

Multiple GPU Indexes

For projects needing specific torch+torchvision+torchaudio:

[tool.uv.sources]
torch = { index = "pytorch-cu126" }
torchvision = { index = "pytorch-cu126" }
torchaudio = { index = "pytorch-cu126" }

Quick Reference