Very true. Floating point bugs are hard to find, because there's often no way to compute a more accurate answer. Herbgrind was our attempt at helping track down a root cause once you knew floating point was the problem---that might be the case if, for example, you changed from double to single precision and suddenly the result was way off. But Herbgrind is pretty high overhead; you'd want some other tool to tell you that floating point was a problem to begin with.