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134 lines
3.0 KiB
Markdown
134 lines
3.0 KiB
Markdown
# 🏁 Single-Process Prototype — Implementation Summary
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**Status:** ✅ Complete
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**Date:** October 22, 2025
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**Branch:** `8-single-process-prototype`
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---
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## Overview
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The single-process prototype implements a **discrete event simulation (DES)** of a 3×3 urban grid with five intersections, realistic vehicle behavior, and fully synchronized traffic lights. Everything runs under one process, laying the groundwork for the distributed architecture in Phase 3.
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---
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## Core Architecture
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### **SimulationEngine**
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Drives the DES loop with a priority queue of timestamped events — vehicles, lights, crossings, and periodic stats updates. Handles five intersections (Cr1–Cr5) and six event types.
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**Main loop:**
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```
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while (events && time < duration):
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event = nextEvent()
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time = event.timestamp
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handle(event)
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```
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### **VehicleGenerator**
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Spawns vehicles via:
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* **Poisson arrivals** (λ = 0.5 veh/s) or fixed intervals
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* **Probabilistic routes** from E1–E3
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* **Type distribution**: 20% BIKE, 60% LIGHT, 20% HEAVY
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### **StatisticsCollector**
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Tracks system-wide and per-type metrics: throughput, avg. wait, queue sizes, light cycles — updated every 10 s and at simulation end.
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---
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## Model Highlights
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* **Vehicle** – type, route, timings, lifecycle.
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* **Intersection** – routing tables, traffic lights, queues.
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* **TrafficLight** – red/green cycles with FIFO queues.
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* **Event** – timestamped, comparable; 6 types for all DES actions.
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---
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## Configuration (`simulation.properties`)
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```properties
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simulation.duration=60.0
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simulation.arrival.model=POISSON
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simulation.arrival.rate=0.5
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vehicle.bike.crossingTime=1.5
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vehicle.light.crossingTime=2.0
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vehicle.heavy.crossingTime=4.0
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statistics.update.interval=10.0
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```
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**Speed logic:**
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`t_bike = 0.5×t_car`, `t_heavy = 2×t_car`.
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---
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## Topology
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```
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E1→Cr1→Cr4→Cr5→S
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E2→Cr2→Cr5→S
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E3→Cr3→S
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Bi-dir: Cr1↔Cr2, Cr2↔Cr3
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```
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---
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## Results
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**Unit Tests:** 7/7 ✅
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**60-Second Simulation:**
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* Generated: 22 vehicles
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* Completed: 5 (22.7%)
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* Avg system time: 15.47 s
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* Throughput: 0.08 veh/s
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* All lights & intersections operational
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**Performance:**
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~0.03 s real-time run (≈2000× speed-up), < 50 MB RAM.
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---
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## Code Structure
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```
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sd/
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├── engine/SimulationEngine.java
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├── model/{Vehicle,Intersection,TrafficLight,Event}.java
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├── util/{VehicleGenerator,StatisticsCollector}.java
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└── config/SimulationConfig.java
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```
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---
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## Key Flow
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1. Initialize intersections, lights, first events.
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2. Process events chronologically.
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3. Vehicles follow routes → queue → cross → exit.
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4. Lights toggle, queues drain, stats update.
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5. Print summary and performance metrics.
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---
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## Next Steps — Phase 3
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* Split intersections into independent **processes**.
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* Add **socket-based communication**.
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* Run **traffic lights as threads**.
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* Enable **distributed synchronization** and fault handling.
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---
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## TL;DR
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Solid single-process DES ✅
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Everything’s working — traffic lights, routing, vehicles, stats.
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Ready to go distributed next. |