Levenberg-Marquardt is a popular alternative to the Gauss-Newton method of finding the minimum of a function that is a sum of squares of nonlinear functions,
Let the Jacobian of be denoted , then the Levenberg-Marquardt method searches in the direction given by the solution to the equations
where are nonnegative scalars and is the identity matrix. The method has the nice property that, for some scalar related to , the vector is the solution of the constrained subproblem of minimizing subject to (Gill et al. 1981, p. 136).
The method is used by the command FindMinimum[f, x, x0] when given the Method -> LevenbergMarquardt option.