List Labeling Array (LLA)

A C implementation of a List Labeling Array data structure that maintains a sorted array with O(log²n) insertion time and O(log²n) amortized elements moved per insertion.

Key Features

• O(log²n) insertion time
• O(log²n) amortized elements moved per insertion
• Density-based rebalancing strategy
• Memory-efficient implementation
• Configurable parameters for balancing

Implementation Details

Data Structure

The LLA consists of two main components:

1. A sorted array storing the elements
2. A balancing tree that manages the density of array segments

Key Parameters

• N: Size of the array
• C: Capacity factor
• TAU_0: Initial density threshold
• TAU_D: Maximum density threshold

Core Operations

• create_lla(N, C, TAU_0, TAU_D): Creates a new LLA instance
• insert(lla, x): Inserts element x while maintaining sorted order
• cleanup_lla(lla): Frees all allocated memory

Building and Running

Prerequisites

• GCC compiler
• Make
• entr (for auto-rebuild feature)

Building

make

Running

./program

Auto-Rebuild and Run

To automatically rebuild and run when source files change:

./watch.sh

Cleaning

make clean

Performance Testing

The project includes a performance test suite that:

• Measures insertion time complexity
• Verifies O(log²n) amortized time
• Provides correlation analysis with theoretical complexity
• Reports detailed timing statistics

Project Structure

.
├── lla.h          # Header file with declarations
├── lla.c          # Implementation file
├── main.c         # Test driver and performance measurements
├── Makefile       # Build configuration
└── watch.sh       # Auto-rebuild script

Dependencies

• entr for auto-rebuild feature:
  • macOS: brew install entr
  • Ubuntu/Debian: sudo apt-get install entr
  • Fedora: sudo dnf install entr

Usage Example

#include "lla.h"

int main() {
    // Create LLA with N=1024, C=8, TAU_0=0.5, TAU_D=0.75
    lla *my_lla = create_lla(1024, 8, 0.5, 0.75);
    
    // Insert elements
    insert(my_lla, 10);
    insert(my_lla, 5);
    insert(my_lla, 15);
    
    // Print current state
    print_lla(my_lla);
    
    // Cleanup
    cleanup_lla(&my_lla);
    return 0;
}

References

1. McCauley, S., Moseley, B., Niaparast, A., & Singh, S. (2023). Online List Labeling with Predictions. arXiv:2305.10536

2. Bender, M. A., & Hu, H. (2007). An adaptive packed-memory array. ACM Transactions on Database Systems, 32(4), 26-es. https://doi.org/10.1145/1292609.1292616