⚡ Bolt: Optimize BuildCandidateRoutes LINQ allocation overhead

.jules/bolt.md

@@ -13,3 +13,6 @@
 ## 2026-05-14 - O(N^2) LINQ Evaluation inside Nested Routing Loop
 **Learning:** `BuildCandidateRoutes` runs repeatedly during capacity bidding (inside a `while (true)` loop). In its original form, it performed `context.Demand.Where(...).Select(...)` within the body of an outer `foreach` loop over `context.Supply`. This led to the `Demand` dictionary being repeatedly iterated and filtered on *every* producer iteration, causing severe O(P * C) allocation and evaluation bottlenecks.
 **Action:** When a method processes combinations from two collections using nested loops, always pre-compute the filtered/projected sequences (e.g., `ToList()`) *outside* of the outer loop.
+## 2026-05-17 - O(N*M) LINQ Evaluation in `BuildCandidateRoutes` Inner Loops
+**Learning:** In routing services (`TemporalNetworkSimulationEngine.cs` and `MixedRouting.cs`), `BuildCandidateRoutes` used LINQ filtering (`Where`, `Select`) on dictionaries (`context.Supply`, `context.Demand`) directly within the inner scopes of nested `foreach` loops. Because the outer loop iterated over producing nodes and the inner over consuming nodes, this led to extreme O(P*C) enumerator allocations and redundant LINQ evaluations.
+**Action:** Always pre-compute and materialize `.ToList()` filtered source collections outside of outer iteration loops when processing combinatorics (like routes between producers and consumers).

patch_bolt.diff

@@ -0,0 +1,48 @@
+--- src/MedWNetworkSim.App/Services/TemporalNetworkSimulationEngine.cs
++++ src/MedWNetworkSim.App/Services/TemporalNetworkSimulationEngine.cs
+@@ -1941,10 +1941,16 @@
+     {
+         var routes = new List<RouteCandidate>();
+
+-        foreach (var producerNodeId in context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key))
++        // ⚡ Bolt: Pre-compute active producers and consumers outside the nested loops
++        // to avoid O(P * C) redundant LINQ evaluations and allocations during routing.
++        var activeProducers = context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key).ToList();
++        var activeConsumers = context.Demand
++            .Where(pair => pair.Value > Epsilon)
++            .Select(pair => pair.Key)
++            .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId))
++            .ToList();
++
++        foreach (var producerNodeId in activeProducers)
+         {
+-            foreach (var consumerNodeId in context.Demand
+-                .Where(pair => pair.Value > Epsilon)
+-                .Select(pair => pair.Key)
+-                .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId)))
++            foreach (var consumerNodeId in activeConsumers)
+             {
+--- src/MedWNetworkSim.App/Services/MixedRouting.cs
++++ src/MedWNetworkSim.App/Services/MixedRouting.cs
+@@ -825,10 +825,16 @@
+     {
+         var routes = new List<RouteCandidate>();
+-        foreach (var producerNodeId in context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key))
++
++        // ⚡ Bolt: Pre-compute active producers and consumers outside the nested loops
++        // to avoid O(P * C) redundant LINQ evaluations and allocations during routing.
++        var activeProducers = context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key).ToList();
++        var activeConsumers = context.Demand
++            .Where(pair => pair.Value > Epsilon)
++            .Select(pair => pair.Key)
++            .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId))
++            .ToList();
++
++        foreach (var producerNodeId in activeProducers)
+         {
+-            foreach (var consumerNodeId in context.Demand
+-                .Where(pair => pair.Value > Epsilon)
+-                .Select(pair => pair.Key)
+-                .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId)))
++            foreach (var consumerNodeId in activeConsumers)
+             {

patch_bolt2.diff

@@ -0,0 +1,25 @@
+--- src/MedWNetworkSim.App/Services/MixedRouting.cs
++++ src/MedWNetworkSim.App/Services/MixedRouting.cs
+@@ -825,12 +825,18 @@
+     {
+         var routes = new List<RouteCandidate>();
+-        foreach (var producerNodeId in context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key))
++
++        // ⚡ Bolt: Pre-compute active producers and consumers outside the nested loops
++        // to avoid O(P * C) redundant LINQ evaluations and allocations during routing.
++        var activeProducers = context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key).ToList();
++        var activeConsumers = context.Demand
++            .Where(pair => pair.Value > Epsilon)
++            .Select(pair => pair.Key)
++            .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId))
++            .ToList();
++
++        foreach (var producerNodeId in activeProducers)
+         {
+-            foreach (var consumerNodeId in context.Demand
+-                .Where(pair => pair.Value > Epsilon)
+-                .Select(pair => pair.Key)
+-                .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId)))
++            foreach (var consumerNodeId in activeConsumers)
+             {
+                 if (Comparer.Equals(producerNodeId, consumerNodeId))

src/MedWNetworkSim.App/Services/MixedRouting.cs

@@ -825,12 +825,19 @@ public static void ApplyLocalAllocations(RoutingTrafficContext context, NetworkM
     private static List<RouteCandidate> BuildCandidateRoutes(RoutingTrafficContext context, NetworkState state, AllocationContext allocationContext)
     {
         var routes = new List<RouteCandidate>();
-        foreach (var producerNodeId in context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key))
+
+        // ⚡ Bolt: Pre-compute active producers and consumers outside the nested loops
+        // to avoid O(P * C) redundant LINQ evaluations and allocations during routing.
+        var activeProducers = context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key).ToList();
+        var activeConsumers = context.Demand
+            .Where(pair => pair.Value > Epsilon)
+            .Select(pair => pair.Key)
+            .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId))
+            .ToList();
+
+        foreach (var producerNodeId in activeProducers)
         {
-            foreach (var consumerNodeId in context.Demand
-                .Where(pair => pair.Value > Epsilon)
-                .Select(pair => pair.Key)
-                .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId)))
+            foreach (var consumerNodeId in activeConsumers)
             {
                 if (Comparer.Equals(producerNodeId, consumerNodeId))
                 {

src/MedWNetworkSim.App/Services/TemporalNetworkSimulationEngine.cs

@@ -1941,12 +1941,18 @@ private static List<RouteCandidate> BuildCandidateRoutes(
     {
         var routes = new List<RouteCandidate>();
 
-        foreach (var producerNodeId in context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key))
+        // ⚡ Bolt: Pre-compute active producers and consumers outside the nested loops
+        // to avoid O(P * C) redundant LINQ evaluations and allocations during routing.
+        var activeProducers = context.Supply.Where(pair => pair.Value > Epsilon).Select(pair => pair.Key).ToList();
+        var activeConsumers = context.Demand
+            .Where(pair => pair.Value > Epsilon)
+            .Select(pair => pair.Key)
+            .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId))
+            .ToList();
+
+        foreach (var producerNodeId in activeProducers)
         {
-            foreach (var consumerNodeId in context.Demand
-                .Where(pair => pair.Value > Epsilon)
-                .Select(pair => pair.Key)
-                .Where(nodeId => context.MeetingDemandEligibleNodeIds.Contains(nodeId)))
+            foreach (var consumerNodeId in activeConsumers)
             {
                 if (Comparer.Equals(producerNodeId, consumerNodeId))
                 {