7constexpr double pi = 3.14159265358979323846;
8constexpr double inv_pi = 0.31830988618379067153;
9constexpr double e = 2.71828182845904523536;
10constexpr double sqrt2 = 1.41421356237309504880;
11constexpr double sqrt3 = 1.73205080756887729352;
12constexpr double inv_sqrt3 = 0.57735026918962576450;
13constexpr double phi = 1.61803398874989484820;