Mike Day writes: > Is the relatively low speed a necessary price > for recent improvements in the robustness of > p. in J6.01? > If you have a lot of quadratics to solve, using a special method rather than p. will almost certainly be faster.
I have no idea how p. works: presumably it could use special case analysis for the solutions in radicals (degree at most 4). Finding polynomial roots in general is a hard problem because of instability issues: small changes in the coefficients can cause large changes in the roots. The celebrated example is Wilkinson's polynomial, referred to in the release notes and described in more detail at: http://en.wikipedia.org/wiki/Wilkinson's_polynomial I regard p. for root finding as a useful first approximation, but I would not rely on it in general. For example, it is a poor way of calculating eigenvalues, even though mathematically they are the roots of the characteristic polynomial. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
