⚖️ SJF, Max-Min & Mixed Strategy: A Comparison 📊

👋 Hey devs!

We’ve all come across scheduling—whether it’s planning your own tasks or how a CPU schedules different processes. It’s a pretty common topic in computer science, and when I first learned about it, I had a lot of questions. Mainly: Which scheduling strategy actually works best? 🤔

At first, all the different strategies—SJF, Max-Min, and Mixed—felt a little confusing. So I decided to break things down in a simple way that’s easy to understand.

In this post, we’ll look at three quick and quirky battle scenarios to see how these strategies work in real life!

🔥 The Battle Begins!

We pit Shortest Job First (SJF), Maximum-Minimum (Max-Min), and a Mixed Strategy against each other in a CPU scheduling showdown!

• SJF ⏳: Prioritizes small jobs first, perfect for quickly clearing short tasks — but big jobs might starve.
• Max-Min 💪: Gives priority to big jobs, ensuring heavy processes don't wait — but small jobs can get delayed.
• Mixed Strategy ⚖️: Aims for balance, preventing both small and large jobs from starving, but adds complexity.

🔗 Jump to Battle Scenarios!

1️⃣ Scenario 1: SJF – Small Jobs Rule!

2️⃣ Scenario 2: Max-Min – VIP Jobs First!

3️⃣ Scenario 3: Mixed Strategy – The Best of Both Worlds!

🚀 Scenario 1: SJF vs. Max-Min: The Ultimate Restaurant Serve 🍔🔥

👨‍🍳 Welcome to CPU Diner – Where Scheduling Can Make or Break Your Hunger!

At CPU Diner, three customers arrive simultaneously (AT = 0) and order different meals. Let's see how our two chefs handle their orders!

🍟 The Customers Arrive

🍳 Chef SJF’s Strategy (Shortest Job First)

⏩ SJF Says: "Yo, let's get the fastest orders done first!"

Execution Order in SJF:

1️⃣ Fries (2 mins)

2️⃣ Burger (5 mins)

3️⃣ Pizza (10 mins)

Total Values for SJF:

✅ Total Finish Time (TFT) = 17 mins

✅ Total Waiting Time (TWT) = 0 + 2 + 7 = 9 mins

✅ Total Turnaround Time (TAT) = 2 + 7 + 17 = 26 mins

Execution Order:

1️⃣ Fries 🍟 (2 mins) → (Done! Alex is happy 😍)

2️⃣ Burger 🍔 (5 mins) → (Done! Bob is satisfied 😌)

3️⃣ Pizza 🍕 (10 mins) → (Finally! Charlie eats 😐)

🔥 Chef Max-Min’s Strategy (Longest Job First)

🐢 Max-Min Says: "Naaaah, let's tackle the BIGGEST meal first. Let’s make ‘em wait! 😈"

Execution Order in Max-Min:

1️⃣ Pizza (10 mins)

2️⃣ Burger (5 mins)

3️⃣ Fries (2 mins)

Total Values for Max-Min:

❌ Total Finish Time (TFT) = 17 mins (same as SJF, but less efficient!)

❌ Total Waiting Time (TWT) = 0 + 10 + 15 = 25 mins (WAY higher than SJF! 🔥🔥🔥)

❌ Total Turnaround Time (TAT) = 10 + 15 + 17 = 42 mins (MUCH worse! 💀)

Execution Order:

1️⃣ Pizza 🍕 (10 mins) → (Charlie is happy, but Alex & Bob are starving! 😵)

2️⃣ Burger 🍔 (5 mins) → (Bob FINALLY eats… but he's annoyed 🤬)

3️⃣ Fries 🍟 (2 mins) → (Alex could’ve eaten long ago… now he’s fuming! 😡🔥)

📊 SJF vs. Max-Min: The Ultimate Scoreboard

🔥 FINAL VERDICT: SJF WINS! 🎉

• SJF serves food quickly & keeps customers happy. 🍟🍔
• Max-Min leaves people STARVING! 😡🔥
• Short jobs should NEVER have to wait behind long jobs!

🥇 Who Wins?

✅ Winner: SJF! 🎉

• SJF keeps everyone happy because orders are served in a balanced way.
• Max-Min is a disaster for small orders—short tasks suffer!

🚀 Lesson: In CPU scheduling (or in real life), serving small tasks first speeds up the whole system!

💡 Moral of the Story:

"If you want efficiency, always serve short tasks first. Don't make people wait for no reason!" 🚀

🏁 Scenario 2: The CPU Olympics – A High-Priority Race! 🏃‍♂️💨

💡 Scenario Setup:

Imagine a coding competition where three teams submit programs for execution. The judge (CPU) schedules them based on execution time.

But this time, longer tasks are more important (e.g., AI training, simulations).

⏳ The Competitors & Their Programs

🍳 Chef SJF’s Strategy (Shortest Job First)

⏩ SJF Says: "Let's finish small programs first, THEN handle the big guys!"

Execution Order in SJF:

1️⃣ Simple Calculator (2 mins)

2️⃣ Data Processing (4 mins)

3️⃣ Machine Learning Model (8 mins)

Total Values for SJF:

❌ Total Finish Time (TFT) = 14 mins (Big task delayed! 😱)

❌ Total Waiting Time (TWT) = 0 + 2 + 6 = 8 mins

❌ Total Turnaround Time (TAT) = 2 + 6 + 14 = 22 mins

🔥 Chef Max-Min’s Strategy (Longest Job First)

🐢 Max-Min Says: "Screw the tiny tasks, let’s start with the BIG BOYS! 💪"

Execution Order in Max-Min:

1️⃣ Machine Learning Model (8 mins)

2️⃣ Data Processing (4 mins)

3️⃣ Simple Calculator (2 mins)

Total Values for Max-Min:

✅ Total Finish Time (TFT) = 14 mins (Same, but ML model finished EARLIER! 🚀)

✅ Total Waiting Time (TWT) = 0 + 8 + 12 = 20 mins (More waiting, but worth it! 😏)

✅ Total Turnaround Time (TAT) = 8 + 12 + 14 = 34 mins (Worse for small tasks, but ML finishes FIRST!)

📊 SJF vs. Max-Min: The Ultimate Scoreboard

🔥 FINAL VERDICT: MAX-MIN WINS! 🎉 (For Priority Tasks)

• If your goal is to finish BIGGER, more important tasks EARLIER, Max-Min is the KING! 👑
• If you just want the smallest tasks done fast, go for SJF.

💡 Moral of the Story:

🔹 SJF is better for getting everything done faster. 🏎️

🔹 Max-Min is better when HIGH-priority tasks MUST finish first. 🔥

📌 Scenario 3: The Grand Hotel CPU 🏨

Imagine a hotel with a single elevator that serves VIP guests (big jobs) and regular guests (small jobs).

• VIP guests (long burst time) pay more 💰, so they need priority.
• Regular guests (short burst time) just want to reach their rooms quickly.
• Some guests arrive later than others (different arrival times).

🔢 Guest List (Processes)

🥩 Case 1: SJF – Small First, Chaos Ensues!

👨‍🍳 SJF Says: "Short jobs first, always!"

Execution Order:

1️⃣ Speedy Coder (3 mins)

2️⃣ Data Analyst (4 mins)

3️⃣ Gamer (6 mins)

4️⃣ AI Researcher (10 mins)

Total Values for SJF:

✅ Total Finish Time (TFT) = 23 mins (Not bad! 😎)

✅ Total Waiting Time (TWT) = 0 + 2 + 4 + 11 = 17 mins

✅ Total Turnaround Time (TAT) = 3 + 6 + 10 + 21 = 40 mins

😱 BUT WAIT… The VIP AI Researcher waited 11 mins before even starting!! BAD for priority jobs. 😬

🔥 Case 2: Max-Min – Big First, Everyone Waits!

💪 Max-Min Says: "BIG jobs get priority, sorry small fries!"

Execution Order:

1️⃣ AI Researcher (10 mins)

2️⃣ Gamer (6 mins)

3️⃣ Data Analyst (4 mins)

4️⃣ Speedy Coder (3 mins)

Total Values for Max-Min:

❌ Total Finish Time (TFT) = 23 mins (Same, but worse TAT!)

❌ Total Waiting Time (TWT) = -2 + 7 + 15 + 20 = 40 mins (WHAT!? 😭)

❌ Total Turnaround Time (TAT) = 8 + 13 + 19 + 23 = 63 mins (Yikes!)

😬 BAD NEWS: Speedy Coder waited FOREVER. AI Researcher finished early, but short jobs suffered HARD.

🔥🔥 Case 3: MIXED STRATEGY – Balance Both!

🧠 New Rule:

• Biggest job shouldn’t starve.
• Shortest jobs should get quick wins.
• Medium jobs? Let’s balance!

Execution Order:

1️⃣ Speedy Coder (3 mins) ✅ (Quick win!)

2️⃣ AI Researcher (10 mins) ✅ (Gets priority!)

3️⃣ Data Analyst (4 mins) ✅

4️⃣ Gamer (6 mins) ✅

Total Values for Mixed Strategy:

✅ Total Finish Time (TFT) = 23 mins (Same! But better balance!)

✅ Total Waiting Time (TWT) = 0 + 1 + 12 + 14 = 27 mins (WAY better!)

✅ Total Turnaround Time (TAT) = 3 + 11 + 16 + 20 = 50 mins (Better than Max-Min!)

🎉 BEST OF BOTH WORLDS!

• AI Researcher doesn’t wait forever.
• Speedy Coder gets fast service.
• Medium jobs don’t get bullied.

📊 FINAL SHOWDOWN: The Scoreboard

🏆 FINAL VERDICT: MIXED STRATEGY WINS!

• Best balance for ALL tasks.
• VIP jobs get priority without starving small tasks.
• Still maintains a good finish time.

Sometimes it’s not just about the smallest or the biggest tasks—it’s about finding the right balance ⚖️. SJF works great for small and quick jobs ⚡, Max-Min is ideal when you need to prioritize big, important ones 💪, and the Mixed Strategy gives you a flexible, all-round solution that handles both 🚀.

This post was just a simple idea to compare these strategies in an easy way ✍️. I covered three cases since these were part of what I studied for my exam. If you have more scenarios or thoughts, feel free to share them in the comments 💬—I'd be happy to add more!