Greedy First Run

lib/core.ts

@@ -1361,11 +1361,21 @@ export class TinyHyperGraphSolver extends BaseSolver {
     state.currentRouteId = undefined
   }
 
+  protected isEstablishingInitialSolution(): boolean {
+    return !this.bestSolvedStateSnapshot
+  }
+
   computeG(currentCandidate: Candidate, neighborPortId: PortId): number {
     const { state } = this
 
     const nextRegionId = currentCandidate.nextRegionId
 
+    if (this.isEstablishingInitialSolution()) {
+      return (
+        currentCandidate.g + (this.problem.portPenalty?.[neighborPortId] ?? 0)
+      )
+    }
+
     const regionCache = state.regionIntersectionCaches[nextRegionId]
     const segmentGeometry = this.populateSegmentGeometryScratch(
       nextRegionId,

lib/section-solver/index.ts

@@ -684,6 +684,10 @@ class TinyHyperGraphSectionSearchSolver extends TinyHyperGraphSolver {
     return super.getStartingNextRegionId(routeId, startingPortId)
   }
 
+  protected override isEstablishingInitialSolution(): boolean {
+    return false
+  }
+
   override resetRoutingStateForRerip() {
     if (!this.fixedSnapshot) {
       super.resetRoutingStateForRerip()

tests/solver/single-layer-region-cost.test.ts

@@ -45,12 +45,21 @@ const createProblem = (): TinyHyperGraphProblem => ({
   regionNetId: new Int32Array(2).fill(-1),
 })
 
-const getCrossingCost = (regionAvailableZMask: number, portZ: number) => {
+const getCrossingCost = (
+  regionAvailableZMask: number,
+  portZ: number,
+  hasInitialSolution = true,
+) => {
   const solver = new TinyHyperGraphSolver(
     createTopology(regionAvailableZMask, portZ),
     createProblem(),
   )
 
+  if (hasInitialSolution) {
+    solver.state.unroutedRoutes = []
+    solver.onAllRoutesRouted()
+  }
+
   solver.state.currentRouteNetId = 0
   solver.appendSegmentToRegionCache(0, 0, 2)
 
@@ -67,6 +76,10 @@ const getCrossingCost = (regionAvailableZMask: number, portZ: number) => {
   )
 }
 
+test("initial solution routing ignores same-layer crossing costs", () => {
+  expect(getCrossingCost(1 << 0, 0, false)).toBe(0)
+})
+
 test("same-layer crossings in known single-layer regions are rejected as candidates", () => {
   const topLayerCrossingCost = getCrossingCost(1 << 0, 0)
   const bottomLayerCrossingCost = getCrossingCost(1 << 1, 1)