Conditions for Digit Stability in Iterative Methods Using the Redundant Number Representation

McInerney, Ian (2022) Conditions for Digit Stability in Iterative Methods Using the Redundant Number Representation. [MIMS Preprint]

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Abstract

Iterative methods play an important role in science and engineering applications, with uses ranging from linear system solvers in finite element methods to optimization solvers in model predictive control. Recently, a new computational strategy for iterative methods called ARCHITECT was proposed by Li et al. in [1] that uses the redundant number representation to create "stable digits" in the Most-significant Digits (MSDs) of an iterate, allowing the future iterations to assume the stable MSDs have not changed their value, eliminating the need to recompute them. In this work, we present a theoretical analysis of how these "stable digits" arise in iterative methods by showing that a Fejér monotone sequence in the redundant number representation can develop stable MSDs in the elements of the sequence as the sequence grows in length. This property of Fejér monotone sequences allows us to expand the class of iterative methods known to have MSD stability when using the redundant number representation to include any fixed-point iteration of a contractive Lipschitz continuous function. We then show that this allows for the theoretical guarantee of digit stability not just in the Jacobi method that was previously analyzed by Li et al. in [2], but also in other commonly used methods such as Newton's method.

Item Type:	MIMS Preprint
Uncontrolled Keywords:	Digit stability, redundant number representation, fixed-point iterations.
Subjects:	MSC 2010, the AMS's Mathematics Subject Classification > 65 Numerical analysis
Depositing User:	Dr Ian McInerney
Date Deposited:	09 May 2022 11:42
Last Modified:	09 May 2022 11:42
URI:	https://eprints.maths.manchester.ac.uk/id/eprint/2853

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