TPU available: true when there are no TPUs

[dalmia]

🐛 Bug

I am using a DGX machine (and so, no TPUs), but on initiating Trainer, it logs TPU available: True. This ends up returning Missing XLA configuration when I run my script.

To Reproduce

Code sample

Simply running the following lines on my machine:

>> trainer = pl.Trainer(gpus=[0])                                                                                                                 
GPU available: True, used: True
TPU available: True, using: 0 TPU cores

Expected behavior

>> trainer = pl.Trainer(gpus=[0])                                                                                                                 
GPU available: True, used: True
TPU available: False, using: 0 TPU cores

Environment

* CUDA:
        - GPU:
                - Tesla V100-SXM2-32GB
        - available:         True
        - version:           10.2
* Packages:
        - numpy:             1.18.2
        - pyTorch_debug:     False
        - pyTorch_version:   1.6.0
        - pytorch-lightning: 0.9.0
        - tensorboard:       2.2.0
        - tqdm:              4.45.0
* System:
        - OS:                Linux
        - architecture:
                - 64bit
                - 
        - processor:         x86_64
        - python:            3.6.9
        - version:           #168-Ubuntu SMP Wed Jan 16 21:00:45 UTC 2019

[Borda]

sounds like some misconfiguration issue, are interested in sending a PR? 🐰

[dalmia]

Sure. I realized that the bug is in this script.

Specifically:

try:
    import torch_xla.core.xla_model as xm
except ImportError:
    XLA_AVAILABLE = False
else:
    XLA_AVAILABLE = True

So, if the environment has torch_xla installed but no TPU, then this error is thrown. If I use an environment without torch_xla, it works fine. So, is this something that should be fixed in the codebase or something that the user should take care of? @Borda

[Borda]

yes, we had the XLA detection as a temporal solution as we did not expect someone would install XLA without having TPU...
so, pls send a PR, I think that we have this patter in several files...

[stale]

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