I do physics simulations and I generally use -ffast-math. For most simulation types, proper algorithms are stable with respect to small floating-point errors (t

I do physics simulations and I generally use -ffast-math. For most simulation types, proper algorithms are stable with respect to small floating-point errors (this has been a subject of research for decades). The extra speed provided by imprecise math allows for bigger, longer simulations, which ultimately means more accuracy than what is lost in the floating-point operations.