,
Xiang Huang
Creative Commons Attribution 4.0 International license
Current analog complexity theory, built on the General-Purpose Analog Computer (GPAC) model and polynomial ODEs, allows unbounded state variables - an assumption that is physically unrealistic for chemical reaction networks and other laboratory-scale analog computers. We develop a bounded analog complexity theory in which all state variables remain in compact intervals and physical time is the only diverging resource.
Our main technical contribution is bounded surrogate compilation, a compilation framework that transforms unbounded polynomial ODE systems into bounded ones while preserving computational limits and time-to-precision guarantees. We prove that on compact domains, physical time and trajectory length differ by at most constant factors; combined with the Bournez-Graça-Pouly characterization, this yields: bounded-GPAC polynomial time equals 𝐏 over the reals.
We exhibit concrete constructions demonstrating fine-grained bounded time complexity - a tunable polynomial-degree family, a Lambert-W-based system achieving Θ(rlog r) time-to-precision (where r is the desired precision parameter, in nats: |x(t)-α| < e^{-r}), and an iterated-logarithm tower realizing arbitrarily high complexity classes - all for the task of computing the constant 1. We show that bounded GPACs are closed under exponentiation (α^β) with time complexity equal to the harder input, and that the full GPAC-to-CRN compilation pipeline preserves time complexity class via a low-pass filter analysis of readout modules.
@InProceedings{chen_et_al:LIPIcs.DNA.32.14,
author = {Chen, Ho-Lin and Huang, Xiang},
title = {{Bounded Analog Complexity}},
booktitle = {32nd International Conference on DNA Computing and Molecular Programming (DNA 32)},
pages = {14:1--14:22},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-444-4},
ISSN = {1868-8969},
year = {2026},
volume = {387},
editor = {Scalise, Dominic and Schweller, Robert},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DNA.32.14},
URN = {urn:nbn:de:0030-drops-267841},
doi = {10.4230/LIPIcs.DNA.32.14},
annote = {Keywords: Analog computation, GPAC, bounded complexity, chemical reaction networks, polynomial ODE}
}