LightGBM on the mac

[TomFinley]

So, LightGBM is a little funky on the Mac. In order for it to work you have to install gcc (usually via brew install gcc), though you don't have to actually build anything (which is enormously confusing). I guess this is an issue we should raise with whoever comes up with the LightGBM nuget package.

This seems like something that the documentation should be more explicit about, but really, this is something that could be handled by Python itself -- if the DLL import fails in Mac, could it not catch that failure, and provide a more helpful error message than this?

Error: *** System.DllNotFoundException: 'Unable to load DLL 'lib_lightgbm': The specified module or one of its dependencies could not be found.

Maybe this could be easy? I imagine that the DLL is being loaded from .NET side, but perhaps you could have a "preload" check in the Python code, to see if the DLL load will probably work, or something.

[montebhoover]

Comes from this url: https://review.docs.microsoft.com/en-us/nimbusml/installationguide?view=nimbusml-py&branch=smoke-test

[montebhoover]

Closing, as the immediate problem has been fixed in https://github.com/MicrosoftDocs/mlnet-pr/pull/29, and the underlying issue is being addressed in dotnet/machinelearning#1282.