Better initial guesses for reinitialized iterative solvers

[ChrisRackauckas]

https://scicomp.stackexchange.com/questions/23323/role-of-initial-guess-for-iterative-linear-solver https://krypy.readthedocs.io/en/latest/krypy.utils.html#krypy.utils.hegedus http://math.aalto.fi/~kuiduhut/spkry.pdf https://fenicsproject.org/qa/7253/convergence-of-iterative-solver-with-initial-guess/

[YingboMa]

https://www.cs.mcgill.ca/~chris/pub/PaiS02c.pdf page 6