v0.0.4 Strict acceptance

What's new

Accept a link only on strict label improvement (u_i > u_j + c_a): labels and costs are unchanged, but this keeps the strategy acyclic - the paper's nonstrict >= admits zero-cost board-alight cycles on which one-pass loading loses flow (see TestBoardAlightLoopConservation).

For the more information see the reference: 90f2562