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LINC: Decoupling Local Consequence Scoring from Hidden Matching in Constructive Neural Routing
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Proposes LINC, a decoder-side candidate scoring architecture that explicitly computes one-step routing consequences (travel, waiting, slack, timing) and scores them with a state-conditioned shared linear comparator, improving PolyNet/POMO on TSP, CVRP, and CVRPTW.
Problem
Constructive neural routing solvers must implicitly reconstruct deterministic one-step transition consequences (travel, waiting, timing slack, capacity) from a hidden decoder context, which hurts feasibility-sensitive routing and generalization under distribution and scale shift.
Approach
Compute explicit candidate-level local consequence features from the known transition and score them with a shared linear comparator whose weights are generated from the decoder context and a feasible-set summary, combined with standard context-key attention via a gate.
Key results
- On Solomon-100 CVRPTW, LINC unguided achieves 7.3% gap vs. 13.8% for PolyNet; on Homberger-200 it reaches 14.71% vs. 38.14%.
- No-retraining scale transfer at CVRPTW n=1000: LINC 42472.66 vs PolyNet 86869.17 (-51.11%); CVRP n=1000: -47.07% relative to PolyNet.
- TSP100 gap 0.000% for both PolyNet and LINC; CVRP100 gap reduced from 0.50% to 0.48%, so gains on TSP/CVRP in-distribution are small.
Surprising findings
- On TSP and CVRP in-distribution, gains over PolyNet are marginal (e.g., TSP100 0.000% for both), with the advantage concentrated on CVRPTW and larger scales.
- Removing GateAttn slightly improves the objective (-0.03%), indicating that component is neutral in the ablation.
Limitations
- Autoregressive single-route-prefix construction cannot coordinate multiple routes in parallel and may suffer early commitment or route imbalance.
- Consequence features must be hand-specified for each routing variant.
- Only one-step consequences are used; no multi-step lookahead.
Experimental setup
Datasets: TSPLIB50-200 CVRPXML100 Solomon-100 Homberger-200 synthetic TSP100/CVRP100 random instances procedural CVRPTW generator
Benchmarks: Synthetic-100 CVRPTW Solomon-100 Homberger-200 TSP100 TSP150 CVRP100 CVRP150 TSPLIB50-200 CVRPXML100 Homberger-400/600/1000 (scale transfer) TSP500/1000 and CVRP500/1000 (scale transfer)
Metrics: objective (mean travel distance) optimality gap wall-clock time
Baselines: POMO PolyNet Poppy SGBS DPDP MDAM DACT BQ-NCO Concorde LKH3 HGS PyVRP
Builds on: POMO PolyNet Attention Model SGBS BQ-NCO
Closest papers by meaning
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