[lamontcg]

That is a pretty hyperbolic statement, but I found that e.g. Brent's rootfinding algorithm on wikipedia was not good and looped rather than exiting when using an error tolerance of EPS (blowing up in the maxiteration check), while finding a more battlehardened implementation and copying the algorithm worked much better. I never did the work to determine exactly where the bugs were in the algorithm in the wikipedia page though.