boost::math::constants::two_div_pi<>() is unavailable in older boost
boost::math::constants::two_div_pi<>() is unavailable in older boost

kapadia/vexcl,ddemidov/vexcl,Poulpy21/vexcl,ddemidov/vexcl,Poulpy21/vexcl,kapadia/vexcl,Poulpy21/vexcl