[modernize] Refactor NumericDiff to use if constexpr recursion Change-Id: I54ad1cec6924e4f4b5275056df7496c2e226f244
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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