I've merged latest changes in kmath into the dev:
https://github.com/mipt-npm/kmath/commit/4b7bd3d174b70cebff1ba936b378ff386d878c74. It includes symbolic API (which is a bit awkward because of double symbol declaration, but in general rather powerful ( we can later add more safe single-variable and double-variable extensions for safety). Also it include a prototype of fitting with CM gradient descent engine (I plan to add other engines later). From the point of user API it is the finest thing I saw so far since it contains type-safe autodiff, likelihood/chi-squared builder and enginer configuration in compact and fully configurable shape. Of course we will need to work more on this and include autodiff from
@breandan.