The Multi-X algorithm proposed in paper: Daniel Barath and Jiri Matas, Multi-class model fitting by energy-minimization and mode-seeking, European Conference on Computer Vision, 2018.
It is available at http://openaccess.thecvf.com/content_ECCV_2018/papers/Daniel_Barath_Multi-Class_Model_Fitting_ECCV_2018_paper.pdf
The used version of OpenCV is 3.10.