Primary Secondary Clustering

Duration: 3 min

This video lesson is available to enrolled students.

Return to /learn/NIACL-AO-IT-SPECIALIST/data-structure-it-specialist/hashing/open-addressing-probing/asset-primary-secondary-clustering after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. Quantitative Aptitude: Ratio and Proportion (Ratios), Data Interpretation, Mixture and Alligation, Permutation and Combination, Number System, Sequence and Series (Series), Speed Time and Distance, Speed Mathematics and Basic Mathematics, Algebra, Percentage, Profit and Loss, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Time and Work, Mensuration and Geometry, Partnership
  2. Reasoning Ability: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Seating Arrangements, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Directions (Direction Test), Ranking, Order and Sequence, Syllogisms, Blood Relations, Puzzle Solving (Puzzles), Inequality, Machine Input-Output
  3. English Language: Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Construction, Pronoun, Preposition, Conjunction, Adverb, Verb, Modals, Articles, Determiner, Interjection
  4. General Awareness: Evolution of Indian Banking (Banking & Financial Awareness), GK- Current Affairs, Static General Knowledge, Indian Economy
  5. C Concepts + MCQs (IT Specialist): C Programming by Yash Sir, C Language Core
  6. Java (IT Specialist): Java
  7. Python (IT Specialist): Python for Placements by Yash Sir, Python Basics
  8. OOPs (IT Specialist): Object Oriented Programming (OOPS)
  9. DBMS (IT Specialist): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
  10. SQL (IT Specialist): SQL
  11. Software Engineering (IT Specialist): Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  12. Data Structure (IT Specialist): Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  13. Operating System (IT Specialist): Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  14. Compiler Design (IT Specialist): 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
  15. Computer Architecture (IT Specialist): Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Multiprocessors, Programming the Basic Computer
  16. Data Communication & Networking (IT Specialist): 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
  17. Descriptive Test (Main Exam): English Writing Ability
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The lecture details two critical failure modes in open addressing hash tables: primary clustering and secondary clustering. The instructor begins by defining primary clustering, noting it is especially prevalent in linear probing. He explains that when a collision occurs, a record is moved to the next available cell, creating a contiguous cluster of occupied cells. He illustrates this concept with a diagram of a hash table array, marking a collision point and writing out the probe sequence "LH", "L+1", "L+2", "L+3", "L+4". He draws arrows to show how any new record hashed to a position within this cluster causes the cluster to grow, significantly increasing access times.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces primary clustering as a major failure mode of open addressing based hash tables. He explains that in linear probing, a record involved in a collision is always moved to the next available hash table cell subsequent to the position given by its hash function. He draws a long rectangular box representing the hash table and marks an 'X' to indicate a collision. He writes "LH" and then "L+1", "L+2", "L+3", "L+4" below the box to represent the linear probe sequence. He draws curved arrows above the box to visualize how new keys landing in the cluster cause it to grow in size by one cell, creating a contiguous block of occupied cells.

  2. 2:00 – 3:17 02:00-03:17

    The lecture transitions to secondary clustering, which occurs more generally with open addressing modes including linear probing and quadratic probing. The instructor underlines the text stating that a low-quality hash function may cause many keys to hash to the same location. He then demonstrates quadratic probing by writing the sequence "L", "L+1^2", "L+2^2", "L+3^2", "L+4^2" below the hash table diagram. He draws curved arrows to show how keys jump to different locations based on the square of the probe number, but notes that if they start at the same location, they follow the same probe sequence, leading to slow access times.

The video effectively contrasts primary and secondary clustering. Primary clustering creates large contiguous blocks in linear probing, while secondary clustering affects both linear and quadratic probing when hash functions are poor. The instructor uses diagrams and written formulas to clarify how probe sequences differ and how clusters form, providing a clear visual aid for understanding these performance degradation issues in hash tables.

Loading lesson…