Time-efficient implementation of the safe PI function–based algorithms for Tarski* and Tarski

Ascertain whether the O(log n)-query algorithm for Tarski*(n,3), and the induced O(log^2 n)-query algorithm for Tarski(n,4), can be implemented with efficient time complexity rather than relying on the currently non–time-efficient safe partial-information framework and brute-force steps.

Background

The paper achieves optimal query complexity for Tarski(n,4) and improved bounds for higher dimensions via a new framework based on safe partial-information (PI) functions. However, the resulting algorithms are not time-efficient for two reasons explicitly noted by the authors: (1) the safe PI function game framework is not currently time-efficient, and (2) selecting good query points uses brute-force counting arguments.

The authors explicitly elevate the question of time efficiency to an open problem, asking whether these query-efficient algorithms can be implemented to run efficiently in time.

References

It is an important open problem whether the algorithm can be implemented efficiently in terms of time complexity.

The Mystery Deepens: On the Query Complexity of Tarski Fixed Points  (2604.00268 - Chen et al., 31 Mar 2026) in Section 7 (Conclusion and Discussion)