BatchSizeFinder throws KeyError: 'limit_eval_batches'

Author: drusmanbashirCreated Nov 10, 2023Updated Sep 9, 2026

Labelsbugduplicatehelp wantedtunerver: 2.1.xrepro needed

Bug description

Using the latest Lightning-AI v 2.1

I have added vanilla BatchSizeFinder as a callback to my lightningmodule. After it finishes finding the correct batchsize, it breaks while calling function batch_size_scaling. The error message is:

File ~/miniconda3/envs/dl/lib/python3.10/site-packages/lightning/pytorch/tuner/batch_size_scaling.py:155, in __scale_batch_restore_params(trainer, params)
    153     stage = trainer.state.stage
    154     assert stage is not None
--> 155     setattr(trainer, f"limit_{stage.dataloader_prefix}_batches", params["limit_eval_batches"])
    157 loop.load_state_dict(deepcopy(params["loop_state_dict"]))
    158 loop.restarting = False

On debugging the params variable only has the following keys:

dict_keys(['loggers', 'callbacks', 'max_steps', 'limit_train_batches', 'limit_val_batches', 'loop_state_dict'])

So indeed the limit_eval_batches key does not exist in my lightningmodule. Happy to provide more info if needed.

Thanks

What version are you seeing the problem on?

v2.1

How to reproduce the bug

No response

Error messages and logs

# Error messages and logs here please

Environment

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More info

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Source: Lightning-AI/pytorch-lightning

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