rafaelglikis/dynamic-connectivity

There is given an undirected graph G = (V, E) from which edges are deleted one at a time. Questions like "Are the vertices u and v in the same connected component?" have to be answered in constant time.

An On-Line Edge-Deletion Problem POC

Abstract

There is given an undirected graph G = (V, E) from which edges are deleted one at a time. Questions like "Are the vertices u and v in the same connected component?" have to be answered "on-line".

This is an implementation of a decremental dynamic algorithm [ES81] which maintains a data structure in which each question is answered in constant time and for which the total time involved in answering q questions and maintaining the data structure is O(q+|V|*|E|), and O(q+|E|*log(|E|)) for acyclic graphs.

Requirements

• boost graph library
• openmp
• cmake

How to use it

• Create graph and initialize it
• Make deletions
• Make queries
• Repeat

Example

#include <iostream>
#include "../incl/graph_types/DynamicGraph.h"

int main()
{
    // Create graph the bgl way
    DynamicGraph G;
    add_edge(0, 1, G);
    add_edge(0, 2, G);
    add_edge(2, 3, G);
    add_edge(4, 5, G);
    add_edge(4, 6, G);
    add_edge(6, 5, G);
    add_edge(7, 8, G);

    // Initialize dynamic Graph
    G.init();

    // Delete edge
    G.deleteEdge(7, 8);
    
    if(G.areConnected(7, 8)) {
        std::cout << "Vertices 7 and 8 are connected!" << std::endl;
    }
    else {
        std::cout << "Vertices 7 and 8 not are connected!" << std::endl;
    }
}

Compile

mkdir cmake-build 
cd cmake-build 
cmake ..
cd ..
cmake --build cmake-build

Usage

Usage:

dynamic_connectivity ACTION* [OPTION]*

Example:

dynamic_connectivity benchmark --random -v 500 -e 1000 -d 50 -q 50

Test:

--test                       run all tests

Benchmarks:

--benchmark                  run benchmark specified benchmarks
--path                       run benchmark with path graph
--tree                       run benchmark with tree graph
--random                     run benchmark with random graph
--path-complete              run benchmark with path of complete subgraphs

Benchmark options:

-v [ --vertices ] arg (=100) specify number of vertices
-e [ --edges ] arg (=460)    specify number of edges (only for random graphs)
-d [ --deletions ] arg (=50) specify number of vertices
-q [ --queries ] arg (=50)   specify number of vertices

Examples:

--example                    run an example at src/example.cpp

Help:

--help                       produce help message

Visualization:

dynamic_connectivity --example
./visualize-example.sh

References

• [ES81] S. Even and Y. Shiloach, "An On-Line Edge-Deletion Problem", Journal of the ACM, 28(1):1-4, 1981