🚀 ACA Dynamic Instruction Scheduling Simulator

An interactive educational simulator for visualizing and comparing Scoreboard and Tomasulo's Algorithm in modern processors.

Developed for the Advanced Computer Architecture course at Amirkabir University of Technology.

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📖 Overview

The ACA Dynamic Instruction Scheduling Simulator is a cycle-accurate educational tool designed to help students understand how dynamic instruction scheduling works inside modern CPUs.

The simulator supports two of the most important scheduling algorithms:

• Scoreboard

  • Centralized hazard detection
  • No register renaming
  • WAR/WAW hazards cause stalls

• Tomasulo's Algorithm

  • Distributed reservation stations
  • Register renaming
  • Common Data Bus (CDB)
  • Eliminates WAR and WAW hazards

The project provides a modern graphical interface that allows users to create custom instruction sequences, configure processor resources, execute simulations cycle-by-cycle, and visualize every stage of execution.

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✨ Features

📂 Scenario Management

• Create custom instruction scheduling scenarios
• Configure functional units and execution latencies
• Built-in educational examples
• Save, edit, duplicate, and delete scenarios
• Import / Export scenarios (.aca)

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📊 Simulation Visualization

Gantt Chart

Visual timeline showing:

• Issue
• Read Operands
• Execute
• Write Back
• Waiting/Stall periods

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Timing Table

Cycle-accurate execution table including:

Column	Description
Issue	Instruction issue cycle
RO	Read operands
EX	Execute
WB	Write back

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Hazards Analysis

Automatically detects:

• ✅ RAW (Read After Write)
• ✅ WAR (Write After Read)
• ✅ WAW (Write After Write)

with detailed information about dependent instructions.

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Performance Dashboard

Displays:

• Total execution cycles
• Number of instructions
• Average instruction latency
• IPC / Issue rate
• Functional unit utilization

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Instruction Statistics

Pie chart showing instruction distribution by type:

• LOAD
• STORE
• ADD
• SUB
• MUL
• DIV

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Tomasulo Visualization

When Tomasulo mode is selected, the simulator additionally displays:

• Reservation Stations
• Register Status Table
• Register Tags
• Common Data Bus (CDB) activity

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Simulation Log

Cycle-by-cycle textual execution log showing:

• Instruction issued
• Operand reads
• Execution start/end
• Write-back events
• Hazard detection
• Functional unit allocation

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Animated CPU Clock

A synchronized CPU clock updates every simulation cycle to provide an intuitive visualization of processor timing.

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🎮 Interactive Controls

The simulator supports both automatic and manual execution.

Controls

• ▶ Play
• ⏸ Pause
• ⏭ Step Forward
• ⏮ Step Backward
• 🎚 Cycle Slider
• ⚡ Clock Speed Control

Users can jump to any simulation cycle or replay the execution from any point.

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⚖ Supported Scheduling Algorithms

Feature	Scoreboard	Tomasulo
Dynamic Scheduling	✅	✅
Centralized Control	✅	❌
Reservation Stations	❌	✅
Register Renaming	❌	✅
RAW Detection	✅	✅
WAR Elimination	❌	✅
WAW Elimination	❌	✅
Common Data Bus (CDB)	❌	✅

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🏗 Project Architecture

Backend

Built with Python + FastAPI

src/
├── instruction.py      # Instruction parser and model
├── utils.py            # Utilities and configuration loader
├── scoreboard.py       # Scoreboard simulator
├── tomasulo.py         # Tomasulo simulator
├── simulator.py        # Simulation orchestrator
└── api.py              # REST API

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Frontend

Built with Flutter + BLoC

lib/
├── models/
├── screens/
│   ├── onboarding/
│   ├── dashboard/
│   ├── scenario/
│   ├── simulator/
│   └── compare/
├── widgets/
├── bloc/
├── services/
└── core/

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⚙ Installation

Prerequisites

Backend

• Python 3.8+
• FastAPI
• Uvicorn

Frontend

• Flutter 3.0+

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Backend Setup

git clone https://github.com/yourusername/aca_project.git

cd aca_project

pip install fastapi uvicorn python-multipart

uvicorn src.api:app --reload --host 0.0.0.0 --port 8000

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Frontend Setup

cd frontend

flutter pub get

flutter run

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🚀 Usage

1. Create a Scenario

1. Click New Scenario
2. Enter a scenario name
3. Select scheduling algorithm
4. Configure functional units
5. Configure execution latencies
6. (Optional) Configure reservation stations
7. Enter assembly instructions
8. Save or run the scenario

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2. Run Simulation

1. Open a saved scenario
2. Click Run Simulation
3. Control execution using Play/Pause or manual stepping
4. Navigate between visualization tabs

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3. Compare Algorithms

Select two scenarios and press Compare to view side-by-side comparisons of:

• Execution timeline
• Total cycles
• Performance metrics
• Hazard statistics

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📝 Supported Assembly Instructions

Instruction	Format	Example
LOAD	LOAD Rd offset(Rs)	LOAD R1 0(R2)
STORE	STORE Rs offset(Rbase)	STORE R3 4(R2)
ADD	ADD Rd Rs1 Rs2	ADD R4 R1 R5
SUB	SUB Rd Rs1 Rs2	SUB R6 R7 R8
MUL	MUL Rd Rs1 Rs2	MUL R3 R1 R4
DIV	DIV Rd Rs1 Rs2	DIV R8 R2 R9

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Example Program

LOAD R1 0(R2)
MUL R3 R1 R4
ADD R5 R3 R6
SUB R1 R7 R8
MUL R9 R1 R10
ADD R11 R9 R12
STORE R11 0(R13)

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🌐 REST API

Endpoints

Method	Endpoint	Description
GET	/	Health check
POST	/run_simulation	Execute a simulation

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Example Request

{
  "mode": "scoreboard",
  "instructions": [
    "LOAD R1 0(R2)",
    "MUL R3 R1 R4"
  ],
  "config": {
    "registers": [
      "R0",
      "R1",
      "R2",
      "R3",
      "R4",
      "R5"
    ],
    "functional_units": {
      "ALU": {
        "count": 2,
        "latency": 2
      },
      "MULT": {
        "count": 1,
        "latency": 10
      },
      "LOAD_STORE": {
        "count": 1,
        "latency": 2
      }
    }
  }
}

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🧪 Sample Programs

Program 1 — Hazard Demonstration

LOAD R1 0(R2)
MUL R3 R1 R4
ADD R5 R3 R6
SUB R1 R7 R8
MUL R9 R1 R10
ADD R11 R9 R12
STORE R11 0(R13)

Expected hazards:

• RAW ×3
• WAR ×1
• WAW ×1

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Program 2 — RAW Hazard

MUL R1 R2 R3
ADD R4 R1 R5

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Program 3 — WAW Hazard

MUL R1 R2 R3
SUB R1 R4 R5

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Program 4 — WAR Hazard

ADD R1 R2 R3
MUL R4 R1 R5
ADD R1 R6 R7

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⚙ Default Configuration

Functional Units

Unit	Count	Latency	Operations
ALU	2	2	ADD, SUB, AND, OR, XOR
MULT	1	10	MUL, DIV
LOAD/STORE	1	2	LOAD, STORE

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Tomasulo Reservation Stations

Functional Unit	Stations
ALU	3
MULT	2
LOAD/STORE	2

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🔧 Troubleshooting

Backend won't start

pip install fastapi uvicorn python-multipart

netstat -ano | findstr :8000

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Frontend cannot connect

Verify that:

• Backend is running
• API URL is correct
• CORS is enabled
• Port 8000 is available

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Type Casting Errors

Ensure:

• Functional unit counts are integers
• Latencies are integers
• Configuration maps are correctly formatted

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👨‍💻 Technologies Used

Backend

• Python
• FastAPI

Frontend

• Flutter
• Dart
• flutter_bloc

Visualization

• Custom Flutter Widgets
• Interactive Gantt Charts
• Data Tables
• Charts

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👤 Author

Reza Tahmasbi

Advanced Computer Architecture Course

Amirkabir University of Technology

Summer 1405

Version 1.1

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📄 License

This project is intended solely for educational purposes.

All rights reserved.

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📬 Contact

For questions, bug reports, or suggestions, please contact the author through mailing: rezatahmasbi@aut.ac.ir