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A Faster Algorithm for Finding Tarski Fixed Points

Published: 11 October 2022 Publication History

Abstract

Dang et al. have given an algorithm that can find a Tarski fixed point in a k-dimensional lattice of width n using O(log k n) queries [2]. Multiple authors have conjectured that this algorithm is optimal [2, 7], and indeed this has been proven for two-dimensional instances [7]. We show that these conjectures are false in dimension three or higher by giving an O(log2 n) query algorithm for the three-dimensional Tarski problem. We also give a new decomposition theorem for k-dimensional Tarski problems which, in combination with our new algorithm for three dimensions, gives an O(log2 ⌈k/3⌉ n) query algorithm for the k-dimensional problem.

References

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Ching-Lueh Chang, Yuh-Dauh Lyuu, and Yen-Wu Ti. 2008. The complexity of Tarski’s fixed point theorem. Theor. Comput. Sci. 401, 1–3 (2008), 228–235.
[2]
Chuangyin Dang, Qi Qi, and Yinyu Ye. 2020. Computations and complexities of Tarski’s fixed points and supermodular games. CoRR abs/2005.09836 (2020). Stanford Tech Report version appeared in 2012.
[3]
Chuangyin Dang and Yinyu Ye. 2018. On the Complexity of a Class of Discrete Fixed Point Problems Under the Lexicographic Ordering. Technical Report. City University of Hong Kong, CY2018-3, 17 pages.
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Chuangyin Dang and Yinyu Ye. 2018. On the complexity of an expanded Tarski’s fixed point problem under the componentwise ordering. Theor. Comput. Sci. 732 (2018), 26–45.
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Chuangyin Dang and Yinyu Ye. 2020. Erratum/correction to “On the complexity of an expanded Tarski’s fixed point problem under the componentwise ordering” [Theor. Comput. Sci. 732 (2018) 26–45]. Theor. Comput. Sci. 817 (2020), 80.
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John Fearnley, Paul W. Goldberg, Alexandros Hollender, and Rahul Savani. 2021. The complexity of gradient descent: CLS = PPAD \(\cap\) PLS. In Proc. of STOC. 46–59.
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  • (2022)The Complexity of Gradient Descent: CLS = PPAD ∩ PLSJournal of the ACM10.1145/356816370:1(1-74)Online publication date: 19-Dec-2022

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  1. A Faster Algorithm for Finding Tarski Fixed Points

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    Published In

    cover image ACM Transactions on Algorithms
    ACM Transactions on Algorithms  Volume 18, Issue 3
    July 2022
    314 pages
    ISSN:1549-6325
    EISSN:1549-6333
    DOI:10.1145/3561945
    • Editor:
    • Edith Cohen
    Issue’s Table of Contents

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    Association for Computing Machinery

    New York, NY, United States

    Publication History

    Published: 11 October 2022
    Online AM: 17 March 2022
    Accepted: 02 February 2022
    Received: 15 June 2021
    Published in TALG Volume 18, Issue 3

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    Author Tags

    1. Query complexity
    2. Tarski fixed points
    3. total function problem

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    • (2022)The Complexity of Gradient Descent: CLS = PPAD ∩ PLSJournal of the ACM10.1145/356816370:1(1-74)Online publication date: 19-Dec-2022

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