> Another downside is that solving this kind of matrix equation gets prohibitively slow when you have a lot of unknowns, which gives rise to the conventional wisdom that individual sketches should be small and simple.
I've gotten quite deep into this, and this is really not a problem in practice[1]
1. FreeCAD's main issues with constraint performance come from a redundant & unnecessary GUI layout algorithm, which falls over with just a few hundred constraints.
2. Eigen's sparse QR decomposition benchmarks at 18s for 2200 constraints, which is really not too bad
3. There are sparse QR decomposition libraries that can handle 500k-1M constraints in about 18s. I can't imagine a CAD sketch with more than a few thousand constraints.
[1]: https://github.com/FreeCAD/FreeCAD/issues/11498#issuecomment...