support for non dask arrays for HyperbandSearchCV

[gioxc88]

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The main changes in this PR are:

1. change to the async def _fit function in dask_ml.model_selection._incremental.py to allow Hyperband to work with non dask arrays

2. fixed default test_size which didn't work with pandas dataframe

[gioxc88]

@stsievert I implemented the changes we discussed. sorry it took so long but I have been busy with other projects.

Cheers Gio

[TomAugspurger]

@stsievert do you have another chance to look at this?

[gioxc88]

Hi @stsievert I agree with you in principle the check should be done on X_train. And sorry for the comments, it was just for me to remember where I made changes. Of course I can remove them.

EDIT: Done

[gioxc88]

does anyone have any idea of what happened with the tests? it's like it's stuck

many thanks

[stsievert]

I'm not sure, but it does look there's a linting issue (both black and isort fail):

Checking black...
black, version 19.10b0
would reformat /home/vsts/work/1/s/dask_ml/model_selection/_incremental.py
would reformat /home/vsts/work/1/s/tests/model_selection/test_hyperband.py
Oh no! 💥 💔 💥
2 files would be reformatted, 98 files would be left unchanged.
Checking black... DONE
Checking isort...
4.3.21
ERROR: /home/vsts/work/1/s/tests/model_selection/test_hyperband.py Imports are incorrectly sorted.
Checking isort... DONE

Try making those lint changes and pushing; that will (likely) resolve the issue.

[hristog]

I've fixed the linting changes locally (and substantially reduced the computational size of the test), but the test_pandas still hangs. I've played around a bit, but haven't been able to identify the root cause yet.