如何解决Google Colab中PyTorch无法启用GPU支持的问题？

Hey there, let's work through this issue where torch.device isn't behaving even though you've installed PyTorch and TensorFlow recognizes your GPU. Here are some targeted fixes to try:

• Verify PyTorch's GPU compatibility first
  Sometimes a "successful install" might actually be the CPU-only version of PyTorch. Run this code snippet to check if CUDA is recognized by PyTorch:

  import torch
  print(torch.cuda.is_available())
  print(torch.cuda.device_count())
  

  If this returns False, you'll need to reinstall PyTorch with the correct GPU-compatible version for Colab's CUDA setup. Use this command (matches Colab's typical CUDA 11.8 environment):

  !pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu118
  

• Restart your Colab Runtime
  After reinstalling PyTorch, it's critical to restart your runtime to load the new libraries properly. Go to the top menu: Runtime > Restart runtime and confirm. Once it's back up, re-run the CUDA check code above.

• Use torch.device with a fallback
  Even if GPU is available, hardcoding torch.device("cuda") can cause errors if there's a misconfiguration. Instead, use this robust pattern to handle both GPU and CPU cases:

  device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
  print(f"Using device: {device}")
  

  This way, you'll automatically fall back to CPU if GPU isn't detected, and get clear feedback on which device is being used.

• Check CUDA version alignment
  TensorFlow might be using a different CUDA setup than your manually installed PyTorch. Confirm Colab's CUDA version with:

  !nvcc --version
  

  Make sure the PyTorch install command matches this version (e.g., cu118 for CUDA 11.8).

Why TensorFlow works but PyTorch doesn't? #

Colab pre-configures TensorFlow to work with GPUs out of the box, but PyTorch requires that you install a version explicitly matched to the environment's CUDA toolkit. A mismatched version will prevent PyTorch from accessing the GPU, even if TensorFlow can see it.

内容的提问来源于stack exchange，提问作者Stepan Yakovenko