SRTF Implementation

Duration: 7 min

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Module outline

  1. About Course: UPPSC Course Overview
  2. Interview Preparation & Guidance: Interview Preparation
  3. Paper 1 | General Hindi: भाषा, लिपि, ध्वनि, वर्ण, अक्षर, स्वर, व्यंजन, मात्रा और संयुक्ताक्षर, वर्तनी, वर्ण-विन्यास, अनुस्वार, अनुनासिक, चंद्रबिंदु और ‘र’ के रूप, शब्द, पद और शब्द-भेद, संज्ञा और सर्वनाम, विशेषण और क्रिया, लिंग, वचन, पुरुष और कारक, काल, वाच्य, वाक्य और वाक्य-भेद, वर्णमाला, समास, संधि, विलोम शब्द, पर्यायवाची शब्द, सामान्य अशुद्धियाँ, अनेक शब्दों के लिए एक शब्द, मुहावरे और लोकोक्तियाँ, अपठित गद्यांश और अपठित पद्यांश, Multi-Topic Content (Cross-Concept Material)
  4. Paper 2 | General Studies: State Wise GK, Polity, Geography, History, GK- Current Affairs
  5. Paper 1 | Programming Language: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++
  6. Paper 1 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, ORDBMS, NoSQL
  7. Paper 1 | Cyber Security: Society, Law & Ethics, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security, Ethical Hacking
  8. Paper 1 | Computer Organization and Architecture: Basics of COA, Programming the Basic Computer, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design
  9. Paper 1 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  10. Paper 1 | Design and Analysis of Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  11. Paper 1 | Data Structures: Introduction to DS, Array, Linked List, Stack, Queue, Tree, Graphs, Hashing
  12. Paper 1 | Discrete Structures and Theory of Logic: Permutation and Combination, Set Theory, Relations, Functions, Propositional and Predicate Logic, Graph Theory, Group Theory
  13. Paper 1 | Software Project Management: Software Project Management
  14. Paper 2 | Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS, Linux OS, Security
  15. Paper 2 | Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment, Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Pushdown Automata & CFG, Complexity Theory
  16. Paper 2 | Artificial Intelligence & High Performance Computing: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Natural Language Processing, Emerging Tech Trends
  17. Paper 2 | Image Processing: Digital Image Fundamentals, Image Enhancement, Image Restoration, Color Image Processing, Image Compression
  18. Paper 2 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  19. Paper 2 | Computer Graphics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing
  20. Paper 2 | Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, HTML Basics, JavaScript-Basics, Java
  21. Paper 2 | Soft Computing: Fuzzy Sets, Artificial Neural Networks, Genetic Algorithms
  22. Paper 2 | Distributed System: Distributed Systems
  23. UPPSC Live Class Recordings: UPPSC Polytechnic Lecturer 2025 (CS)
  24. Previous Year Papers:
  25. Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video lecture focuses on the Shortest Job First (SJF) CPU scheduling algorithm and addresses its primary limitation: the inability to know the exact CPU burst time of a process beforehand. To overcome this, the instructor introduces the concept of predicting the next CPU burst using the exponential averaging technique. The lecture details the mathematical formula for this prediction, defining the variables involved, including the smoothing factor alpha. The instructor provides a step-by-step calculation example on a whiteboard and demonstrates the application of the formula using a process table. Finally, the video concludes by discussing the theoretical nature of this scheme, noting its limitations when burst times vary significantly or remain constant.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The lecture begins with the instructor standing in front of a slide that states, 'As SJF is not implementable, we can use the one technique where we try to predict the CPU burst of the next coming process.' He explains that since the Shortest Job First algorithm requires knowledge of the burst time which is not available, a prediction method is necessary. The slide text further clarifies, 'The method is used as exponential averaging technique, where we consider the previous value and previous prediction.' The instructor emphasizes that this technique relies on historical data to estimate future behavior, setting the stage for the mathematical derivation to follow.

  2. 2:00 – 5:00 02:00-05:00

    The instructor transitions to the core formula displayed on the screen: 'Tau(n+1) = alpa tn + (1- alpa) tau n'. He explains that Tau(n+1) represents the predicted burst time for the next process, tn is the actual burst time of the current process, and tau(n) is the previous predicted burst time. He writes on the whiteboard to illustrate the concept, listing 'M1' with values '250' and '300'. He calculates a resulting value of '275' to show how the average works. He then discusses the parameter 'alpha' (alpha), writing 'alpha = 0', 'alpha = 1', and 'alpha = 0.5' to demonstrate how different weights affect the prediction, explaining that alpha determines the influence of the most recent history versus older history.

  3. 5:00 – 6:40 05:00-06:40

    A table appears on the screen with columns labeled 'Process', 't', and 'tau'. The rows list processes P1, P2, P3, and P4. For P1, the actual time 't' is 10 and the initial 'tau' is 20. The instructor proceeds to calculate the 'tau' values for subsequent processes based on the formula. He writes '15' in the tau column for P2 and '13.5' for P3, showing the iterative nature of the prediction. The video concludes with a slide stating, 'This idea is also more of theoretical importance as most of the time the burst requirement of the coming process may vary by a large extent and if the burst time requirement of all the process is approximately same then there is no advantage of using this scheme.' This highlights the practical limitations of the exponential averaging technique in real-world scenarios.

The video provides a comprehensive overview of how to handle the unpredictability of CPU burst times in the Shortest Job First scheduling algorithm. It moves from identifying the problem to introducing the exponential averaging formula, explaining the role of the alpha parameter, and demonstrating calculations through both whiteboard examples and a process table. The lesson concludes by contextualizing the technique as theoretically important but practically limited when process burst times are inconsistent or uniform.

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