Push-1 is PSPACE-complete, and the automated verification of motion planning gadgets

Fuente: arXiv
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Auteurs principaux: DeStefano, Zachary, Liang, Bufang
Format: Preprint
Publié: 2025
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author DeStefano, Zachary
Liang, Bufang
author_facet DeStefano, Zachary
Liang, Bufang
contents Push-1 is one of the simplest abstract frameworks for motion planning; however, the complexity of deciding if a Push-1 problem can be solved was a several-decade-old open question. We resolve the complexity of the motion planning problem Push-1 by showing that it is PSPACE-complete, and we formally verify the correctness of our constructions. Our results build upon a recent work which demonstrated that Push-1F (a variant of Push-1 with fixed blocks) and Push-k for $k \geq 2$ (a variant of Push-1 where the agent can push $k$ blocks at once) are PSPACE-complete and more generally on the motion-planning-though-gadgets framework. In the process of resolving this open problem, we make two general contributions to the motion planning complexity theory. First, our proof technique extends the standard motion planning framework by assigning the agent a state. This state is preserved when traversing between gadgets but can change when taking transitions in gadgets. Second, we designed and implemented a system, GADGETEER, for computationally verifying the behavior of systems of gadgets. This system is agnostic to the underlying motion planning problem, and allows for formally verifying the correspondence between a low-level construction and a high-level system of gadgets as well as automatically synthesizing gadgets from low-level constructions. In the case of Push-1, we use this system to formally prove that our constructions match our high-level specifications of their behavior. This culminates in the construction and verification of a self-closing door, as deciding reachability in a system of self-closing doors is PSPACE-complete.
format Preprint
id arxiv_https___arxiv_org_abs_2508_17602
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Push-1 is PSPACE-complete, and the automated verification of motion planning gadgets
DeStefano, Zachary
Liang, Bufang
Computational Complexity
Computational Geometry
Push-1 is one of the simplest abstract frameworks for motion planning; however, the complexity of deciding if a Push-1 problem can be solved was a several-decade-old open question. We resolve the complexity of the motion planning problem Push-1 by showing that it is PSPACE-complete, and we formally verify the correctness of our constructions. Our results build upon a recent work which demonstrated that Push-1F (a variant of Push-1 with fixed blocks) and Push-k for $k \geq 2$ (a variant of Push-1 where the agent can push $k$ blocks at once) are PSPACE-complete and more generally on the motion-planning-though-gadgets framework. In the process of resolving this open problem, we make two general contributions to the motion planning complexity theory. First, our proof technique extends the standard motion planning framework by assigning the agent a state. This state is preserved when traversing between gadgets but can change when taking transitions in gadgets. Second, we designed and implemented a system, GADGETEER, for computationally verifying the behavior of systems of gadgets. This system is agnostic to the underlying motion planning problem, and allows for formally verifying the correspondence between a low-level construction and a high-level system of gadgets as well as automatically synthesizing gadgets from low-level constructions. In the case of Push-1, we use this system to formally prove that our constructions match our high-level specifications of their behavior. This culminates in the construction and verification of a self-closing door, as deciding reachability in a system of self-closing doors is PSPACE-complete.
title Push-1 is PSPACE-complete, and the automated verification of motion planning gadgets
topic Computational Complexity
Computational Geometry
url https://arxiv.org/abs/2508.17602