[AutoScheduler] Python based measure callbacks

[comaniac]

The current auto_scheduler callbacks can only be implemented in C++. This PR exposes the interface of measure callbacks to Python so that people can plug in their own callback functions easily.

Note: looks like I cannot pass the SearchPolicy node to the PackedFunc. Specifically, callback_func(policy, inputs, results); results in the type mismatching error. This also prevents us from introducing the Python API for SearchCallback. Any advise is appreciated.

cc @merrymercy @jcf94

[comaniac]

Per offline discussion, we cast the abstract SearchPolicy to the actual instance so that we can pass it to the packed function.

@merrymercy @jcf94 PTAL.

[jcf94]

LGTM. Thanks!

[comaniac]

I also took a look at the SearchCallback (it should be named to something like PreSearchCallback because it will be called once in the beginning of search instead of every round) but decided not to add a Python interface in this PR. Since we don't expose useful SearchPolicy APIs to Python, the Python-based callback can do nothing at this moment. Meanwhile, it's worthwhile to consider PreloadCustomSketchRule as @antinucleon suggested in another PR.

[jcf94]

I also took a look at the SearchCallback (it should be named to something like PreSearchCallback because it will be called once in the beginning of search instead of every round) but decided not to add a Python interface in this PR. Since we don't expose useful SearchPolicy APIs to Python, the Python-based callback can do nothing at this moment. Meanwhile, it's worthwhile to consider PreloadCustomSketchRule as @antinucleon suggested in another PR.

Actually we already have a init_search_callbacks in the constructor function of SearchPolicy which will be called before the search process. And we also have the PreloadCustomSketchRule in our dev repo ...

[comaniac]

Actually we already have a init_search_callbacks in the constructor function of SearchPolicy which will be called before the search process. And we also have the PreloadCustomSketchRule in our dev repo ...

Yeah that's why I bring up this, but my point is these callbacks are C-based instead of Python so there are not that convenient for users to experiment.

[jcf94]

Actually we already have a init_search_callbacks in the constructor function of SearchPolicy which will be called before the search process. And we also have the PreloadCustomSketchRule in our dev repo ...

Yeah that's why I bring up this, but my point is these callbacks are C-based instead of Python so there are not that convenient for users to experiment.

Oh, I find that comment: #7132 (comment)
I agree with your point.
So seems we will need to:

1. Add the PreloadCustomSketchRule which enables users to add their own custom sketches. (And that's what we have already planed long before but didn't take action to bring that here from our dev repo ....)
2. Just like your have added a python based MeasureCallback here, we'd better add a python based SearchCallback for init_search_callbacks.
3. Better re-arrange the rules->push_back(.......) part, maybe also move them to Python as a InitSearchCallback.

Also cc @merrymercy @antinucleon