23,249 research outputs found
Timetabling in constraint logic programming
In this paper we describe the timetabling problem and its solvability in a Constraint Logic
Programming Language. A solution to the problem has been developed and implemented in
ECLiPSe, since it deals with finite domains, it has well-defined interfaces between basic
building blocks and supports good debugging facilities. The implemented timetable was
based on the existing, currently used, timetables at the School of Informatics at out
university. It integrates constraints concerning room and period availability
Automated sequence and motion planning for robotic spatial extrusion of 3D trusses
While robotic spatial extrusion has demonstrated a new and efficient means to
fabricate 3D truss structures in architectural scale, a major challenge remains
in automatically planning extrusion sequence and robotic motion for trusses
with unconstrained topologies. This paper presents the first attempt in the
field to rigorously formulate the extrusion sequence and motion planning (SAMP)
problem, using a CSP encoding. Furthermore, this research proposes a new
hierarchical planning framework to solve the extrusion SAMP problems that
usually have a long planning horizon and 3D configuration complexity. By
decoupling sequence and motion planning, the planning framework is able to
efficiently solve the extrusion sequence, end-effector poses, joint
configurations, and transition trajectories for spatial trusses with
nonstandard topologies. This paper also presents the first detailed computation
data to reveal the runtime bottleneck on solving SAMP problems, which provides
insight and comparing baseline for future algorithmic development. Together
with the algorithmic results, this paper also presents an open-source and
modularized software implementation called Choreo that is machine-agnostic. To
demonstrate the power of this algorithmic framework, three case studies,
including real fabrication and simulation results, are presented.Comment: 24 pages, 16 figure
Automatically improving SAT encoding of constraint problems through common subexpression elimination in Savile Row
The formulation of a Propositional Satisfiability (SAT) problem instance is vital to efficient solving. This has motivated research on preprocessing, and inprocessing techniques where reformulation of a SAT instance is interleaved with solving. Preprocessing and inprocessing are highly effective in extending the reach of SAT solvers, however they necessarily operate on the lowest level representation of the problem, the raw SAT clauses, where higher-level patterns are difficult and/or costly to identify. Our approach is different: rather than reformulate the SAT representation directly, we apply automated reformulations to a higher level representation (a constraint model) of the original problem. Common Subexpression Elimination (CSE) is a family of techniques to improve automatically the formulation of constraint satisfaction problems, which are often highly beneficial when using a conventional constraint solver. In this work we demonstrate that CSE has similar benefits when the reformulated constraint model is encoded to SAT and solved using a state-of-the-art SAT solver. In some cases we observe speed improvements of over 100 times
Automated Diagnosis of Clinic Workflows
Outpatient clinics often run behind schedule due to patients who arrive late
or appointments that run longer than expected. We sought to develop a
generalizable method that would allow healthcare providers to diagnose problems
in workflow that disrupt the schedule on any given provider clinic day. We use
a constraint optimization problem to identify the least number of appointment
modifications that make the rest of the schedule run on-time. We apply this
method to an outpatient clinic at Vanderbilt. For patient seen in this clinic
between March 27, 2017 and April 21, 2017, long cycle times tended to affect
the overall schedule more than late patients. Results from this workflow
diagnosis method could be used to inform interventions to help clinics run
smoothly, thus decreasing patient wait times and increasing provider
utilization
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