sympy/sympy — pull request #7257 by akritas (2014-03-10 20:51:57+00:00)
Title: improved dup_roots_upper_bound; what used to be counter t is now list t

This is the best we can do to improve this implementation without major changes. However, the bounds obtained this way, as powers of 2, are not good enough for VAS. Moreover, and most importantly, the lower bound needs its own implementation for a more accurate value