Fix compute_spillfield_graph dropping isolated trap-bottom vertices - #11
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Isolated cells (e.g. trap bottoms entirely surrounded by masked building cells) produce no flow edges and were silently absent from the returned graph. Add the same add_vertices! call that spillregions already uses to guarantee every grid cell is represented as a vertex. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
compute_spillfield_graphwas filtering out self-loops (correct) but not compensating withadd_vertices!, so isolated cells — concretely, trap bottoms entirely surrounded by masked building cells — were silently missing as vertices from the returned graph.Graphs.add_vertices!(g, xmax * ymax - Graphs.nv(g))before the return, exactly matching the pattern already used in thespillregionsflowgraph construction.Background
_spillfield_flow_edges!intentionally adds self-loop edges(n, n)for trap-bottom and boundary-exit cells that have no inflow, so that_determine_connected_componentscan include them in watershed regions. Callers that build a finalSimpleDiGraphare expected to strip those self-loops and then pad the vertex count.spillregionsdid this correctly;compute_spillfield_graphdid the stripping but skipped the padding.Test plan
Pkg.test())🤖 Generated with Claude Code