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Fixed-point quasi-Newtonian methods. (English) Zbl 0758.65043
This paper studies iterative methods of the form (1) $$x_{k+1}=\Phi(x_ k,E_ k)$$ where $$x_ k\in\mathbb{R}^ n$$, and $$E_ k$$ belongs to some parameter space. Three examples of methods which may be written in this form are given, namely quasi-Newton methods for nonlinear systems, sequential quadratic programming and nonlinear complementarity.
Firstly, the author finds sufficient conditions for the sequence generated by (1) to be convergent to a fixed point of $$\Phi$$ at a linear rate. Then, sufficient conditions for local convergence of the sequence at “ideal” rates are proved (the “ideal” iteration $$x_{k+1}=\Phi(x_ k,E_ *)$$ has an ideal convergence rate $$r_ *$$ which may be found).
The author then discusses convergence theory for least-change fixed-point iterations of quasi-Newton methods and ends by proving local and superlinear convergence results for a particular splitting of $$F(x)$$ for the system $$F(x)=0$$, of the form $$F(x)=F_ 1(x)+F_ 2(x)$$ where, for fixed $$x$$ and some $$B$$, the nonlinear system $$F_ 1(z)+F_ 2(x)+B(z- x)=0$$ is easy to solve for $$z$$.

##### MSC:
 65H10 Numerical computation of solutions to systems of equations 65K05 Numerical mathematical programming methods 90C20 Quadratic programming 90C33 Complementarity and equilibrium problems and variational inequalities (finite dimensions) (aspects of mathematical programming)
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