Complexity Aspects of the Extension of Wagner's Hierarchy to $k$-Partitions

TL;DR

This paper extends the understanding of Wadge reducibility to regular k-partitions of omega-languages, providing a quadratic algorithm for decision and discussing more efficient representations.

Contribution

It finalizes the decision procedure for Wadge reducibility of regular k-partitions with a quadratic algorithm and proposes a more compact language representation.

Findings

Quadratic algorithm for Wadge reducibility decision

Efficient decision procedure for regular k-partitions

More compact representation of omega-languages

Abstract

It is known that the Wadge reducibility of regular $\omega$-languages is efficiently decidable (Krishnan et al., 1995), (Wilke, Yoo, 1995). In this paper we study analogous problem for regular k-partitions of $\omega$-languages. In the series of previous papers (Selivanov, 2011), (Alaev, Selivanov, 2021), (Selivanov, 2012) there was a partial progress towards obtaining an efficient algorithm for deciding the Wadge reducibility in this setting as well. In this paper we finalize this line of research providing a quadratic algorithm (in RAM model). For this we construct a quadratic algorithm to decide a preorder relation on iterated posets. Additionally, we discuss the size of the representation of regular $\omega$-languages and suggest a more compact way to represent them. The algorithm we provide is efficient for the more compact representation as well.