Wrap GNC

[johnwlambert]

Add GNC to the wrapper.

[johnwlambert]

@ProfFan hi Fan, any thoughts on why the Python CI fails here? resolved via Varun's comments

[varunagrawal]

You shouldn't be specifying templates as template<class T>, it should be just template<T>.
Same deal for GncOptimizer.

[johnwlambert]

Got it, thank you Varun

[varunagrawal]

I have a feeling this will compile but won't import since the templates don't have instantiations.

[varunagrawal]

Nitpick: Use a smaller uppercase name like PARAMS and provide either a default via the template list PARAMS = {SomeValue} or use the typedef to declare one (I prefer the former).

Without a template list of typedef, the python module import should error out.

[johnwlambert]

You're right, i checked and it compiled but import didn't work.

I updated the templates, let me know if this is what you had in mind @varunagrawal. Thanks.

[johnwlambert]

weird, even with the updated templates we still get

======================================================================
ERROR: test_NonlinearOptimizer (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_NonlinearOptimizer
Traceback (most recent call last):
  File "/usr/lib/python3.6/unittest/loader.py", line 428, in _find_test_path
    module = self._get_module_from_name(name)
  File "/usr/lib/python3.6/unittest/loader.py", line 369, in _get_module_from_name
    __import__(name)
  File "/home/runner/work/gtsam/gtsam/python/gtsam/tests/test_NonlinearOptimizer.py", line 18, in <module>
    from gtsam import (DoglegOptimizer, DoglegParams,
ImportError: cannot import name 'GncParams'

[johnwlambert]

I'm guessing this is because we were missing GTSAM_EXPORT calls, and because the class wasn't marked as virtual in the .i files. Do we have those steps documented somewhere in gtwrap, along with why they are required? I'm a bit confused about that.

[varunagrawal]

The wrapper appends the template name to disambiguate between instantiations, e.g. PinholeCameraCal3_S2 vs PinholeCameraCal3Bundler. You'll have to import the full name from gtsam import GncOptimizerGncParamsGaussNewtonParams.

Better design would be to use

#include <gtsam/nonlinear/GncParams.h>
template<PARAMS>
virtual class GncParams {
  GncParams(const PARAMS& baseOptimizerParams);
  GncParams();
  void print(const string& str) const;
};

typedef GncParams<gtsam::GaussNewtonParams> GncGaussNewtonParams;
typedef GncParams<gtsam::LevenbergMarquardtParams> GncLMParams;


#include <gtsam/nonlinear/GncOptimizer.h>
template<PARAMS>
virtual class GncOptimizer {
  GncOptimizer(const gtsam::NonlinearFactorGraph& graph,
               const gtsam::Values& initialValues,
               const PARAMS& params);
  gtsam::Values optimize();
};

typedef gtsam::GncOptimizer<gtsam::GncParams<gtsam::GaussNewtonParams>> GncGaussNewtonOptimizer;
typedef gtsam::GncOptimizer<gtsam::GncParams<gtsam::LevenbergMarquardtParams>> GncLMOptimizer;

You should then be able to do

from gtsam import GncLMParams, GncLMOptimizer

[johnwlambert]

Thanks @varunagrawal, looks like all the tests pass now.

[varunagrawal]

Sweet!