Use portable expression for constant 2/sqrt(pi) M_2_SQRTPI is not part of standard C++, replace it with an equivalent expression. gcc immediately folds this and thus generates the same code even at -O0. Change-Id: I5d38e67a4508c1d43a1a8e5f1639f2243cdb143e
Ceres Solver is an open source C++ library for modeling and solving large, complicated optimization problems. It is a feature rich, mature and performant library which has been used in production at Google since 2010. Ceres Solver can solve two kinds of problems.
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