From ab41ea8c39b808a48e576d375a3cb663243cc956 Mon Sep 17 00:00:00 2001
From: ShiboSoftwareDev <shibosoftwaredev@gmail.com>
Date: Fri, 7 Aug 2026 20:23:33 +0200
Subject: [PATCH 1/2] Reject infeasible greedy final routes

---
 lib/core.ts                                   | 33 ++++++++++---------
 ...final-route-single-layer-crossing.snap.svg | 20 ++++-------
 ...-final-route-single-layer-crossing.test.ts |  8 ++---
 3 files changed, 29 insertions(+), 32 deletions(-)

diff --git a/lib/core.ts b/lib/core.ts
index c224a31..bdd19cb 100644
--- a/lib/core.ts
+++ b/lib/core.ts
@@ -587,28 +587,32 @@ export class TinyHyperGraphSolver extends BaseSolver {
       return
     }
 
+    if (currentCandidate.portId === state.goalPortId) {
+      this.onPathFound(currentCandidate)
+      return
+    }
+
     const neighbors =
       topology.regionIncidentPorts[currentCandidate.nextRegionId]
 
     for (const neighborPortId of neighbors) {
       const assignedNetId = state.portAssignment[neighborPortId]
+      const neighborIsGoal = neighborPortId === state.goalPortId
       if (this.isPortReservedForDifferentNet(neighborPortId)) continue
-      if (neighborPortId === state.goalPortId) {
-        if (assignedNetId !== -1 && assignedNetId !== state.currentRouteNetId) {
-          continue
-        }
-        this.onPathFound(currentCandidate)
-        return
-      }
       if (assignedNetId !== -1 && assignedNetId !== state.currentRouteNetId) {
         continue
       }
       if (neighborPortId === currentCandidate.portId) continue
-      if (problem.portSectionMask[neighborPortId] === 0) continue
+      if (!neighborIsGoal && problem.portSectionMask[neighborPortId] === 0) {
+        continue
+      }
 
       const g = this.computeG(currentCandidate, neighborPortId)
       if (!Number.isFinite(g)) continue
-      const h = this.computeH(neighborPortId)
+      if (neighborIsGoal) {
+        this.onPathFound(currentCandidate)
+        return
+      }
 
       const nextRegionId =
         topology.incidentPortRegion[neighborPortId][0] ===
@@ -623,6 +627,7 @@ export class TinyHyperGraphSolver extends BaseSolver {
         continue
       }
 
+      const h = this.computeH(neighborPortId)
       const newCandidate = {
         prevRegionId: currentCandidate.nextRegionId,
         nextRegionId,
@@ -633,11 +638,6 @@ export class TinyHyperGraphSolver extends BaseSolver {
         prevCandidate: currentCandidate,
       }
 
-      if (neighborPortId === state.goalPortId) {
-        this.onPathFound(newCandidate)
-        return
-      }
-
       const candidateHopId = this.getHopId(neighborPortId, nextRegionId)
       if (g >= this.getCandidateBestCost(candidateHopId)) continue
 
@@ -1536,8 +1536,11 @@ export class TinyHyperGraphSolver extends BaseSolver {
 class GreedyFinalRouteSolver extends TinyHyperGraphSolver {
   override computeG(
     currentCandidate: Candidate,
-    _neighborPortId: PortId,
+    neighborPortId: PortId,
   ): number {
+    const constraintAwareCost = super.computeG(currentCandidate, neighborPortId)
+    if (!Number.isFinite(constraintAwareCost)) return constraintAwareCost
+
     return currentCandidate.g
   }
 }
diff --git a/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg b/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
index 5561c9c..064c6a8 100644
--- a/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
+++ b/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
@@ -3,9 +3,8 @@ region: region-0
 z: 0" points="535.5427445183542,175.0677506775068 314.79871889627987,175.0677506775068" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,0.5 0,-0.5" data-type="line" data-label="route-1
 z: 0" points="425.17073170731703,64.69573786646961 425.17073170731703,285.43976348854403" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px" stroke-dasharray="3 3"/></g><g><polyline data-points="0.5,-1.375 -0.5,-1.375" data-type="line" data-label="route: route-0
 region: region-0
-z: 0" points="535.5427445183542,478.5907859078591 314.79871889627987,478.5907859078591" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,-0.875 0,-1.875" data-type="line" data-label="route: route-1
-region: region-0
-z: 0" points="425.17073170731703,368.2187730968219 425.17073170731703,588.9627987188962" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><rect data-type="rect" data-label="region: region-0
+z: 0" points="535.5427445183542,478.5907859078591 314.79871889627987,478.5907859078591" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,-0.875 0,-1.875" data-type="line" data-label="route-1
+z: 0" points="425.17073170731703,368.2187730968219 425.17073170731703,588.9627987188962" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px" stroke-dasharray="3 3"/></g><g><rect data-type="rect" data-label="region: region-0
 net: free
 cost: 0.000
 congestion: 0.000
@@ -37,11 +36,11 @@ same layer X: 0
 trans X: 0
 entry exit X: 0" data-x="0" data-y="0" x="320.31731953683175" y="70.21433850702147" width="209.70682434097063" height="209.70682434097068" fill="rgba(200, 200, 255, 0.1)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-0
 net: free
-cost: 10.567
+cost: 0.000
 congestion: 0.000
-same layer X: 1
+same layer X: 0
 trans X: 0
-entry exit X: 0" data-x="0" data-y="-1.375" x="320.31731953683175" y="373.73737373737373" width="209.70682434097063" height="209.70682434097068" fill="rgba(255, 64, 64, 0.72)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-1
+entry exit X: 0" data-x="0" data-y="-1.375" x="320.31731953683175" y="373.73737373737373" width="209.70682434097063" height="209.70682434097068" fill="rgba(200, 200, 255, 0.1)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-1
 net: free
 cost: 0.000
 congestion: 0.000
@@ -110,13 +109,8 @@ net: 0
 z: 0" data-x="0.5" data-y="-1.375" cx="535.5427445183542" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-0
 port: port-2
 net: 0
-z: 0" data-x="-0.5" data-y="-1.375" cx="314.79871889627987" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-1
-port: port-1
-net: 1
-z: 0" data-x="0" data-y="-0.875" cx="425.17073170731703" cy="368.2187730968219" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-1
-port: port-3
-net: 1
-z: 0" data-x="0" data-y="-1.875" cx="425.17073170731703" cy="588.9627987188962" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g id="crosshair" style="display: none"><line id="crosshair-h" y1="0" y2="640" stroke="#666" stroke-width="0.5"/><line id="crosshair-v" x1="0" x2="640" stroke="#666" stroke-width="0.5"/><text id="coordinates" font-family="monospace" font-size="12" fill="#666"></text></g><script><![CDATA[
+z: 0" data-x="-0.5" data-y="-1.375" cx="314.79871889627987" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route-1
+z: 0" data-x="0" data-y="-1.375" cx="425.17073170731703" cy="478.5907859078591" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g id="crosshair" style="display: none"><line id="crosshair-h" y1="0" y2="640" stroke="#666" stroke-width="0.5"/><line id="crosshair-v" x1="0" x2="640" stroke="#666" stroke-width="0.5"/><text id="coordinates" font-family="monospace" font-size="12" fill="#666"></text></g><script><![CDATA[
               document.currentScript.parentElement.addEventListener('mousemove', (e) => {
                 const svg = e.currentTarget;
                 const rect = svg.getBoundingClientRect();
diff --git a/tests/solver/greedy-final-route-single-layer-crossing.test.ts b/tests/solver/greedy-final-route-single-layer-crossing.test.ts
index 81b3555..49bdecd 100644
--- a/tests/solver/greedy-final-route-single-layer-crossing.test.ts
+++ b/tests/solver/greedy-final-route-single-layer-crossing.test.ts
@@ -10,7 +10,7 @@ import {
   type TinyHyperGraphTopology,
 } from "lib/index"
 
-test("reproduces greedy final routing through a same-layer crossing", () => {
+test("greedy final routing rejects a same-layer crossing", () => {
   const topology: TinyHyperGraphTopology = {
     portCount: 4,
     regionCount: 5,
@@ -66,9 +66,9 @@ test("reproduces greedy final routing through a same-layer crossing", () => {
       solver.state.regionIntersectionCaches[0].existingSameLayerIntersections,
   }).toMatchInlineSnapshot(`
     {
-      "acceptedGreedyFinalRouteOnTimeout": true,
-      "sameLayerCrossings": 1,
-      "solved": true,
+      "acceptedGreedyFinalRouteOnTimeout": undefined,
+      "sameLayerCrossings": 0,
+      "solved": false,
     }
   `)
 })

From 4bea6c5c67226bd009e1eadb9e23951639375b5b Mon Sep 17 00:00:00 2001
From: ShiboSoftwareDev <shibosoftwaredev@gmail.com>
Date: Sat, 8 Aug 2026 00:17:50 +0200
Subject: [PATCH 2/2] Revert "Reject infeasible greedy final routes"

This reverts commit ab41ea8c39b808a48e576d375a3cb663243cc956.
---
 lib/core.ts                                   | 33 +++++++++----------
 ...final-route-single-layer-crossing.snap.svg | 20 +++++++----
 ...-final-route-single-layer-crossing.test.ts |  8 ++---
 3 files changed, 32 insertions(+), 29 deletions(-)

diff --git a/lib/core.ts b/lib/core.ts
index bdd19cb..c224a31 100644
--- a/lib/core.ts
+++ b/lib/core.ts
@@ -587,32 +587,28 @@ export class TinyHyperGraphSolver extends BaseSolver {
       return
     }
 
-    if (currentCandidate.portId === state.goalPortId) {
-      this.onPathFound(currentCandidate)
-      return
-    }
-
     const neighbors =
       topology.regionIncidentPorts[currentCandidate.nextRegionId]
 
     for (const neighborPortId of neighbors) {
       const assignedNetId = state.portAssignment[neighborPortId]
-      const neighborIsGoal = neighborPortId === state.goalPortId
       if (this.isPortReservedForDifferentNet(neighborPortId)) continue
+      if (neighborPortId === state.goalPortId) {
+        if (assignedNetId !== -1 && assignedNetId !== state.currentRouteNetId) {
+          continue
+        }
+        this.onPathFound(currentCandidate)
+        return
+      }
       if (assignedNetId !== -1 && assignedNetId !== state.currentRouteNetId) {
         continue
       }
       if (neighborPortId === currentCandidate.portId) continue
-      if (!neighborIsGoal && problem.portSectionMask[neighborPortId] === 0) {
-        continue
-      }
+      if (problem.portSectionMask[neighborPortId] === 0) continue
 
       const g = this.computeG(currentCandidate, neighborPortId)
       if (!Number.isFinite(g)) continue
-      if (neighborIsGoal) {
-        this.onPathFound(currentCandidate)
-        return
-      }
+      const h = this.computeH(neighborPortId)
 
       const nextRegionId =
         topology.incidentPortRegion[neighborPortId][0] ===
@@ -627,7 +623,6 @@ export class TinyHyperGraphSolver extends BaseSolver {
         continue
       }
 
-      const h = this.computeH(neighborPortId)
       const newCandidate = {
         prevRegionId: currentCandidate.nextRegionId,
         nextRegionId,
@@ -638,6 +633,11 @@ export class TinyHyperGraphSolver extends BaseSolver {
         prevCandidate: currentCandidate,
       }
 
+      if (neighborPortId === state.goalPortId) {
+        this.onPathFound(newCandidate)
+        return
+      }
+
       const candidateHopId = this.getHopId(neighborPortId, nextRegionId)
       if (g >= this.getCandidateBestCost(candidateHopId)) continue
 
@@ -1536,11 +1536,8 @@ export class TinyHyperGraphSolver extends BaseSolver {
 class GreedyFinalRouteSolver extends TinyHyperGraphSolver {
   override computeG(
     currentCandidate: Candidate,
-    neighborPortId: PortId,
+    _neighborPortId: PortId,
   ): number {
-    const constraintAwareCost = super.computeG(currentCandidate, neighborPortId)
-    if (!Number.isFinite(constraintAwareCost)) return constraintAwareCost
-
     return currentCandidate.g
   }
 }
diff --git a/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg b/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
index 064c6a8..5561c9c 100644
--- a/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
+++ b/tests/solver/__snapshots__/greedy-final-route-single-layer-crossing.snap.svg
@@ -3,8 +3,9 @@ region: region-0
 z: 0" points="535.5427445183542,175.0677506775068 314.79871889627987,175.0677506775068" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,0.5 0,-0.5" data-type="line" data-label="route-1
 z: 0" points="425.17073170731703,64.69573786646961 425.17073170731703,285.43976348854403" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px" stroke-dasharray="3 3"/></g><g><polyline data-points="0.5,-1.375 -0.5,-1.375" data-type="line" data-label="route: route-0
 region: region-0
-z: 0" points="535.5427445183542,478.5907859078591 314.79871889627987,478.5907859078591" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,-0.875 0,-1.875" data-type="line" data-label="route-1
-z: 0" points="425.17073170731703,368.2187730968219 425.17073170731703,588.9627987188962" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px" stroke-dasharray="3 3"/></g><g><rect data-type="rect" data-label="region: region-0
+z: 0" points="535.5427445183542,478.5907859078591 314.79871889627987,478.5907859078591" fill="none" stroke="hsla(266, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><polyline data-points="0,-0.875 0,-1.875" data-type="line" data-label="route: route-1
+region: region-0
+z: 0" points="425.17073170731703,368.2187730968219 425.17073170731703,588.9627987188962" fill="none" stroke="hsla(28, 70%, 50%, 0.8)" stroke-width="1px"/></g><g><rect data-type="rect" data-label="region: region-0
 net: free
 cost: 0.000
 congestion: 0.000
@@ -36,11 +37,11 @@ same layer X: 0
 trans X: 0
 entry exit X: 0" data-x="0" data-y="0" x="320.31731953683175" y="70.21433850702147" width="209.70682434097063" height="209.70682434097068" fill="rgba(200, 200, 255, 0.1)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-0
 net: free
-cost: 0.000
+cost: 10.567
 congestion: 0.000
-same layer X: 0
+same layer X: 1
 trans X: 0
-entry exit X: 0" data-x="0" data-y="-1.375" x="320.31731953683175" y="373.73737373737373" width="209.70682434097063" height="209.70682434097068" fill="rgba(200, 200, 255, 0.1)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-1
+entry exit X: 0" data-x="0" data-y="-1.375" x="320.31731953683175" y="373.73737373737373" width="209.70682434097063" height="209.70682434097068" fill="rgba(255, 64, 64, 0.72)" stroke="rgba(128, 128, 128, 0.5)" stroke-width="0.0045301339285714285"/></g><g><rect data-type="rect" data-label="region: region-1
 net: free
 cost: 0.000
 congestion: 0.000
@@ -109,8 +110,13 @@ net: 0
 z: 0" data-x="0.5" data-y="-1.375" cx="535.5427445183542" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-0
 port: port-2
 net: 0
-z: 0" data-x="-0.5" data-y="-1.375" cx="314.79871889627987" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route-1
-z: 0" data-x="0" data-y="-1.375" cx="425.17073170731703" cy="478.5907859078591" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g id="crosshair" style="display: none"><line id="crosshair-h" y1="0" y2="640" stroke="#666" stroke-width="0.5"/><line id="crosshair-v" x1="0" x2="640" stroke="#666" stroke-width="0.5"/><text id="coordinates" font-family="monospace" font-size="12" fill="#666"></text></g><script><![CDATA[
+z: 0" data-x="-0.5" data-y="-1.375" cx="314.79871889627987" cy="478.5907859078591" r="3" fill="hsla(266, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-1
+port: port-1
+net: 1
+z: 0" data-x="0" data-y="-0.875" cx="425.17073170731703" cy="368.2187730968219" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g><circle data-type="point" data-label="route: route-1
+port: port-3
+net: 1
+z: 0" data-x="0" data-y="-1.875" cx="425.17073170731703" cy="588.9627987188962" r="3" fill="hsla(28, 70%, 50%, 1)"/></g><g id="crosshair" style="display: none"><line id="crosshair-h" y1="0" y2="640" stroke="#666" stroke-width="0.5"/><line id="crosshair-v" x1="0" x2="640" stroke="#666" stroke-width="0.5"/><text id="coordinates" font-family="monospace" font-size="12" fill="#666"></text></g><script><![CDATA[
               document.currentScript.parentElement.addEventListener('mousemove', (e) => {
                 const svg = e.currentTarget;
                 const rect = svg.getBoundingClientRect();
diff --git a/tests/solver/greedy-final-route-single-layer-crossing.test.ts b/tests/solver/greedy-final-route-single-layer-crossing.test.ts
index 49bdecd..81b3555 100644
--- a/tests/solver/greedy-final-route-single-layer-crossing.test.ts
+++ b/tests/solver/greedy-final-route-single-layer-crossing.test.ts
@@ -10,7 +10,7 @@ import {
   type TinyHyperGraphTopology,
 } from "lib/index"
 
-test("greedy final routing rejects a same-layer crossing", () => {
+test("reproduces greedy final routing through a same-layer crossing", () => {
   const topology: TinyHyperGraphTopology = {
     portCount: 4,
     regionCount: 5,
@@ -66,9 +66,9 @@ test("greedy final routing rejects a same-layer crossing", () => {
       solver.state.regionIntersectionCaches[0].existingSameLayerIntersections,
   }).toMatchInlineSnapshot(`
     {
-      "acceptedGreedyFinalRouteOnTimeout": undefined,
-      "sameLayerCrossings": 0,
-      "solved": false,
+      "acceptedGreedyFinalRouteOnTimeout": true,
+      "sameLayerCrossings": 1,
+      "solved": true,
     }
   `)
 })