Memory Manager

Link: https://github.com/css186/External-Sorting

Project Description Link to heading

This project is a simulation program for storing, managing records and handling memory allocation and data retrieval using a combination of a hash table and a memory manager.

Here is a breakdown of its components and functionality:

Core Functionality Link to heading

1. Hash Table (HashTable.java)

   • Uses quadratic probing for collision resolution.
   • Stores Record objects that pair seminar IDs with memory handles.
   • Automatically resizes when the load factor exceeds a threshold.

2. Memory Manager(MemManager.java)

   • Manages a dynamic byte array (memory pool) to store serialized seminar data.
   • Uses a free block list (doubly linked list) to track available memory blocks.
   • Allocates memory for new records, splits free blocks if necessary, and merges adjacent blocks when freeing memory.
   • Expands the memory pool incrementally when space runs out.

3. Seminar Object (Seminar.java)

   • Represents seminar data (ID, title, date, location, cost, keywords, etc.).
   • Supports serialization/deserialization to convert objects to/from byte streams for storage in the memory pool.

4. Controller (Controller.java)

   • Coordinates interactions between the hash table and memory manager.
   • Implements operations: insert, search, delete, print (hash table or free blocks).

5. Command Processor (CommandProcessor.java)

   • Parses input files containing commands (insert, search, delete, print).
   • Executes commands by invoking the controller.

Key Workflows Link to heading

1. Insert

   • Serializes the seminar into a byte array.
   • Allocates memory via MemManager and stores the data.
   • Updates the hash table with the ID and memory handle.

2. Search

   • Retrieves the handle from the hash table using the ID.
   • Fetches the byte array from memory and deserializes it into a Seminar object.

3. Delete

   • Removes the ID from the hash table.
   • Marks the associated memory block as free (merged with adjacent blocks if possible).

4. Memory Management

   • Uses a best-fit strategy to allocate memory from the free block list.
   • Merges adjacent free blocks during insert and remove operations to reduce fragmentation.

Program Invocation Link to heading

The program will be invoked from the command line as: java SemMananager {initial-memory-size} {initial-hash-size} {command-file}

• Correct and complete format of input files can be referenced with text files having the _input.txt postfix

Sample Output Link to heading

Takeaways Link to heading

• This program efficiently manages seminar records in memory, ensuring fast lookups (via hashing) and optimized memory usage (via dynamic block allocation/merging).
• Still, code up memory management related functionality is quite challenging and I am very glad that I gave it a try.