333 research outputs found
Learning to Search Feasible and Infeasible Regions of Routing Problems with Flexible Neural k-Opt
In this paper, we present Neural k-Opt (NeuOpt), a novel learning-to-search
(L2S) solver for routing problems. It learns to perform flexible k-opt
exchanges based on a tailored action factorization method and a customized
recurrent dual-stream decoder. As a pioneering work to circumvent the pure
feasibility masking scheme and enable the autonomous exploration of both
feasible and infeasible regions, we then propose the Guided Infeasible Region
Exploration (GIRE) scheme, which supplements the NeuOpt policy network with
feasibility-related features and leverages reward shaping to steer
reinforcement learning more effectively. Additionally, we equip NeuOpt with
Dynamic Data Augmentation (D2A) for more diverse searches during inference.
Extensive experiments on the Traveling Salesman Problem (TSP) and Capacitated
Vehicle Routing Problem (CVRP) demonstrate that our NeuOpt not only
significantly outstrips existing (masking-based) L2S solvers, but also
showcases superiority over the learning-to-construct (L2C) and
learning-to-predict (L2P) solvers. Notably, we offer fresh perspectives on how
neural solvers can handle VRP constraints. Our code is available:
https://github.com/yining043/NeuOpt.Comment: Accepted at NeurIPS 202
Attention, Learn to Solve Routing Problems!
The recently presented idea to learn heuristics for combinatorial
optimization problems is promising as it can save costly development. However,
to push this idea towards practical implementation, we need better models and
better ways of training. We contribute in both directions: we propose a model
based on attention layers with benefits over the Pointer Network and we show
how to train this model using REINFORCE with a simple baseline based on a
deterministic greedy rollout, which we find is more efficient than using a
value function. We significantly improve over recent learned heuristics for the
Travelling Salesman Problem (TSP), getting close to optimal results for
problems up to 100 nodes. With the same hyperparameters, we learn strong
heuristics for two variants of the Vehicle Routing Problem (VRP), the
Orienteering Problem (OP) and (a stochastic variant of) the Prize Collecting
TSP (PCTSP), outperforming a wide range of baselines and getting results close
to highly optimized and specialized algorithms.Comment: Accepted at ICLR 2019. 25 pages, 7 figure
Routing Arena: A Benchmark Suite for Neural Routing Solvers
Neural Combinatorial Optimization has been researched actively in the last
eight years. Even though many of the proposed Machine Learning based approaches
are compared on the same datasets, the evaluation protocol exhibits essential
flaws and the selection of baselines often neglects State-of-the-Art Operations
Research approaches. To improve on both of these shortcomings, we propose the
Routing Arena, a benchmark suite for Routing Problems that provides a seamless
integration of consistent evaluation and the provision of baselines and
benchmarks prevalent in the Machine Learning- and Operations Research field.
The proposed evaluation protocol considers the two most important evaluation
cases for different applications: First, the solution quality for an a priori
fixed time budget and secondly the anytime performance of the respective
methods. By setting the solution trajectory in perspective to a Best Known
Solution and a Base Solver's solutions trajectory, we furthermore propose the
Weighted Relative Average Performance (WRAP), a novel evaluation metric that
quantifies the often claimed runtime efficiency of Neural Routing Solvers. A
comprehensive first experimental evaluation demonstrates that the most recent
Operations Research solvers generate state-of-the-art results in terms of
solution quality and runtime efficiency when it comes to the vehicle routing
problem. Nevertheless, some findings highlight the advantages of neural
approaches and motivate a shift in how neural solvers should be conceptualized
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