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Delete Relaxations for Planning with State-Dependent Action Costs

AAAI Conferences

Supporting state-dependent action costs in planning admits a more compact representation of many tasks. We generalize the additive heuristic and compute it by embedding decision-diagram representations of action cost functions into the RPG. We give a theoretical evaluation and present an implementation of the generalized additive heuristic. This allows us to handle even the hardest instances of the combinatorial Academic Advising domain from the IPPC 2014.


Planning Single-Arm Manipulations with N-Arm Robots

AAAI Conferences

Many robotic systems are comprised of two or more arms. Such systems range from dual-arm household manipulators to factory floors populated with a multitude of industrial robotic arms. While the use of multiple arms increases the productivity of the system and extends dramatically its workspace, it also introduces a number of challenges. One such challenge is planning the motion of the arm(s) required to relocate an object from one location to another. This problem is challenging because it requires reasoning over which arms and in which order should manipulate the object, finding a sequence of valid handoff locations between the consecutive arms and finally choosing the grasps that allow for successful handoffs. In this paper, we show how to exploit the characteristics of this problem in order to construct a planner that can solve it effectively. We analyze our approach experimentally on a number of simulated examples ranging from a 2-arm system operating at a table to a 3-arm system working at a bar and to a 4-arm system in a factory setting.


ICBS: The Improved Conflict-Based Search Algorithm for Multi-Agent Pathfinding

AAAI Conferences

Conflict-Based Search (CBS) and its generalization, Meta-Agent CBS are amongst the strongest newly introduced algorithms for Multi-Agent Path Finding. This paper introduces ICBS, an improved version of CBS. ICBS incorporates three orthogonal improvements to CBS which are systematically described and studied. Experimental results show that each of these improvements reduces the runtime over basic CBS by up to 20x in many cases. When all three improvements are combined, an even larger improvement is achieved, producing state-ofthe art results for a number of domains.


Tight Bounds for HTN Planning with Task Insertion (Extended Abstract)

AAAI Conferences

Hierarchical Task Network (HTN) planning with task insertion (TIHTN planning) is a variant of HTN planning. In HTN planning, the only means to alter task networks is to decompose compound tasks. In TIHTN planning, tasks may also be inserted directly. In this paper we provide tight complexity bounds for TIHTN planning along two axis: whether variables are allowed and whether methods must be totally ordered.


Improved Pattern Selection for PDB Heuristics in Classical Planning (Extended Abstract)

AAAI Conferences

The iPDB approach (Haslum et al. 2007) represents obtained as a result of a local search in the pattern space: the state-of-the-art algorithm to compute pattern databases The extensions of a pattern P are patterns that extend P by (PDBs) (Culberson and Schaeffer 1998) for domain independent one variable that is causally related to a variable in P. For optimal planning.


Automated Transformation of PDDL Representations

AAAI Conferences

This paper describes a system that automatically transforms a PDDL encoding, calls a planner to solve the transformed representation, and translates the solution back into the original representation. The approach involves counting objects that are indistinguishable, rather than treating them as individuals, which eliminates some unnecessary combinatorial explosion.


Empowering Mini-Bucket in Anytime Heuristic Search with Look-Ahead: Preliminary Evaluation

AAAI Conferences

The paper explores the potential of look-ahead methods within the context of AND/OR search in graphical models using the Mini-Bucket heuristic for combinatorial optimization tasks (e.g., weighted CSPS or MAP inference). We study how these methods can be used to compensate for the approximation error of the initially generated Mini-Bucket heuristics, within the context of anytime Branch-And-Bound search.


An Empirical Comparison of Any-Angle Path-Planning Algorithms

AAAI Conferences

We compare five any-angle path-planning algorithms, Theta*, Block A*, Field D*, ANYA, and Any-Angle Subgoal Graphs in terms of solution quality and runtime. Any-angle path-planning is a fairly new research area, and no direct comparison exists between these algorithms. We implement each algorithm from scratch and use similar implementations to provide a fair comparison.


Maximum a Posteriori Estimation by Search in Probabilistic Programs

AAAI Conferences

We introduce an approximate search algorithm for fast maximum a posteriori probability estimation in probabilistic programs, which we call Bayesian ascent Monte Carlo (BaMC). Probabilistic programs represent probabilistic models with varying number of mutually dependent finite, countable, and continuous random variables. BaMC is an anytime MAP search algorithm applicable to any combination of random variables and dependencies. We compare BaMC to other MAP estimation algorithms and show that BaMC is faster and more robust on a range of probabilistic models.


Partial Domain Search Tree for Constraint-Satisfaction Problems

AAAI Conferences

The traditional approach for solving Constraint satisfaction Problems (CSPs) is searching the Assignment Space in which each state represents an assignment to some variables. This paper suggests a new search space formalization for CSPs, the Partial Domain Search Tree (PDST). In each PDST node aunique subset of the original domain is considered, values are excluded from the domains in each node to insure that a given set of constraints is satisfied. We provide theoretical analysis of this new approach showing that searching the PDST is beneficial for loosely constrained problems. Experimental results show that this new formalization is a promising direction for future research. In some cases searching the PDST outperforms the traditional approach by an order of magnitude. Furthermore, PDST can enhance Local Search techniques resulting in solutions that violate up to 30% less constraints.