C++ double division by 0.0 versus DBL_MIN
- by wonsungi
When finding the inverse square root of a double, is it better to clamp invalid non-positive inputs at 0.0 or MIN_DBL? (In my example below double b may end up being negative due to floating point rounding errors and because the laws of physics are slightly slightly fudged in the game.)
Both division by 0.0 and MIN_DBL produce the same outcome in the game because 1/0.0 and 1/DBL_MIN are effectively infinity. My intuition says MIN_DBL is the better choice, but would there be any case for using 0.0? Like perhaps sqrt(0.0), 1/0.0 and multiplication by 1.#INF000000000000 execute faster because they are special cases.
double b = 1 - v.length_squared()/(c*c);
#ifdef CLAMP_BY_0
if (b < 0.0) b = 0.0;
#endif
#ifdef CLAMP_BY_DBL_MIN
if (b <= 0.0) b = DBL_MIN;
#endif
double lorentz_factor = 1/sqrt(b);
double division in MSVC:
1/0.0 = 1.#INF000000000000
1/DBL_MIN = 4.4942328371557898e+307
