fix ptl_bugs in slu_models.py

[jzi040941]

What does this PR do ?

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This PR added fixes for PTL2.0 related SLU bugs in r1.21.0: Val metrics logging, None dataloader issue

Collection:
ASR

Changelog

• correct logging of validation metrics and test_dataloader() function in nemo/collentions/asr/models/slu_models.py updated to handle cases where dataloader is None as done in Fix PTL2.0 related ASR bugs in r1.21.0: Val metrics logging, None dataloader issue #7531

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@stevehuang52 @titu1994

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Additional Information

• Related to val_wer #7450

[stevehuang52]

Thanks for the fix~!

Could you please also change the trainer.strategy=ddp to trainer.strategy=ddp_find_unused_parameters_true in the yaml file? It was giving the following error when I ran with ddp:

RuntimeError: It looks like your LightningModule has parameters that were not used in producing the loss returned by training_step. If this is intentional, you must enable the detection of unused parameters in DDP, either by setting the string value `strategy='ddp_find_unused_parameters_true'` or by setting the flag in the strategy with `strategy=DDPStrategy(find_unused_parameters=True)`.

@jzi040941 did you experience the same issue?

I'll approve once this is resolved.

[jzi040941]

@stevehuang52 Yes, I had same issue with ddp strategy,
it works well after change it to ddp_find_unused_parameters_true

I updated the yaml file, thanks~

[stevehuang52]

LGTM, thanks~!