lightgbm memory spike

[RainFung]

lightgbm.Dataset() always raise a memory spike which make jupyter kernel crash.Like discussed in kaggle, https://www.kaggle.com/c/talkingdata-adtracking-fraud-detection/discussion/55325#319189.

[guolinke]

could you provide more context? How & when you meet the memory spike?
in most cases, the memory spike is caused by the type conversion ( * -> np.float).
So the best practice is to use np.float directly.

[RainFung]

when to use np.float32 directly？ can you give some example

[guolinke]

To avoid any conversions, you should always use np.float32

[StrikerRUS]

Some use cases should be fixed by #2383.