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⚡ Bolt: Optimize O(N^2) timeline.NodeStates lookup inside ApplySimulationOutcomes #269

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⚡ Bolt: Optimize O(N^2) timeline.NodeStates lookup inside ApplySimulationOutcomes #269

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3 changes: 3 additions & 0 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
Expand Up @@ -23,3 +23,6 @@
## 2024-05-23 - Optimize LINQ Allocations in Network Simulation Engine
**Learning:** Found multiple places in `NetworkSimulationEngine.cs` where LINQ `.Count()` and `.Select().Min()` inside inner loops on the simulation path were allocating delegates and enumerators on the hot path (e.g., inside `GetPathRemainingCapacity` and `CountBottleneckResources`).
**Action:** Replaced these LINQ chains with `for` and `foreach` loops respectively to minimize garbage generation during greedy route allocation, reducing allocations during repeated graph evaluations.
## 2026-05-22 - O(N^2) Lookup inside Simulation Updates
**Learning:** In the Avalonia presentation layer, `ApplySimulationOutcomes` in `WorkspacePresentation` was performing an O(N^2) nested lookup by filtering `timeline.NodeStates` inside a loop that iterated over every node in the scene. For large networks, this repeated filtering could freeze the UI during heavy simulation updates.
**Action:** Pre-compute node states into a grouped lookup dictionary outside of the loop, reducing the update bottleneck to O(N + S).
21 changes: 14 additions & 7 deletions src/MedWNetworkSim.Presentation/WorkspacePresentation.cs
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Expand Up @@ -8797,23 +8797,30 @@ private void ApplySimulationOutcomes(IEnumerable<RouteAllocation> allocations, T
var nodesById = network.Nodes.ToDictionary(node => node.Id, Comparer);
if (timeline is not null)
{
// Bolt: Pre-compute node states to optimize O(N^2) timeline.NodeStates lookup
var nodeStatesByNodeId = timeline.NodeStates
.GroupBy(pair => pair.Key.NodeId, Comparer)
.ToDictionary(group => group.Key, group => group.ToList(), Comparer);

foreach (var node in Scene.Nodes)
{
if (!nodesById.TryGetValue(node.Id, out var nodeModel)) continue;
var state = timeline.NodeStates
.Where(pair => Comparer.Equals(pair.Key.NodeId, node.Id))
.Select(pair => pair.Value)
.FirstOrDefault();
var backlogByTraffic = timeline.NodeStates
.Where(pair => Comparer.Equals(pair.Key.NodeId, node.Id) && pair.Value.DemandBacklog > 0d)

var nodeTrafficStates = nodeStatesByNodeId.GetValueOrDefault(node.Id) ?? [];

var state = nodeTrafficStates.Select(pair => pair.Value).FirstOrDefault();

var backlogByTraffic = nodeTrafficStates
.Where(pair => pair.Value.DemandBacklog > 0d)
.GroupBy(pair => pair.Key.TrafficType, pair => pair.Value.DemandBacklog, Comparer)
.Select(group => new KeyValuePair<string, double>(group.Key, group.Sum()))
.ToList();

var pressure = timeline.NodePressureById.GetValueOrDefault(node.Id);
node.MetricsLabel = string.Empty;
node.DetailLines = BuildNodeDetailLines(nodeModel, backlogByTraffic, pressure.Score > 0d ? pressure : null);
UpdateSceneNodeLayout(node, nodeModel, pressure.Score > 0d ? pressure : null, graphRenderer.GetZoomTier(Viewport.Zoom));
node.HasWarning = pressure.Score > 0d || state.DemandBacklog > 0d;
node.HasWarning = pressure.Score > 0d || (state.DemandBacklog > 0d);
}
}
else
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