public class BarabasiAlbertGenerator<V,E> extends Object implements EvolvingGraphGenerator<V,E>
Simple evolving scale-free random graph generator. At each time step, a new vertex is created and is connected to existing vertices according to the principle of "preferential attachment", whereby vertices with higher degree have a higher probability of being selected for attachment.
At a given timestep, the probability p
of creating an edge
between an existing vertex v
and the newly added vertex is
p = (degree(v) + 1) / (|E| + |V|);
where |E|
and |V|
are, respectively, the number
of edges and vertices currently in the network (counting neither the new
vertex nor the other edges that are being attached to it).
Note that the formula specified in the original paper (cited below) was
p = degree(v) / |E|
However, this would have meant that the probability of attachment for any existing isolated vertex would be 0. This version uses Lagrangian smoothing to give each existing vertex a positive attachment probability.
The graph created may be either directed or undirected (controlled by a constructor parameter); the default is undirected. If the graph is specified to be directed, then the edges added will be directed from the newly added vertex u to the existing vertex v, with probability proportional to the indegree of v (number of edges directed towards v). If the graph is specified to be undirected, then the (undirected) edges added will connect u to v, with probability proportional to the degree of v.
The parallel
constructor parameter specifies whether parallel edges
may be created.
Modifier and Type | Field and Description |
---|---|
protected com.google.common.base.Supplier<E> |
edgeFactory |
protected com.google.common.base.Supplier<Graph<V,E>> |
graphFactory |
protected Map<V,Integer> |
index_vertex |
protected int |
init_vertices |
protected List<V> |
vertex_index |
protected com.google.common.base.Supplier<V> |
vertexFactory |
Constructor and Description |
---|
BarabasiAlbertGenerator(com.google.common.base.Supplier<Graph<V,E>> graphFactory,
com.google.common.base.Supplier<V> vertexFactory,
com.google.common.base.Supplier<E> edgeFactory,
int init_vertices,
int numEdgesToAttach,
int seed,
Set<V> seedVertices)
Constructs a new instance of the generator.
|
BarabasiAlbertGenerator(com.google.common.base.Supplier<Graph<V,E>> graphFactory,
com.google.common.base.Supplier<V> vertexFactory,
com.google.common.base.Supplier<E> edgeFactory,
int init_vertices,
int numEdgesToAttach,
Set<V> seedVertices)
Constructs a new instance of the generator, whose output will be an undirected graph,
and which will use the current time as a seed for the random number generation.
|
Modifier and Type | Method and Description |
---|---|
void |
evolveGraph(int numTimeSteps)
Instructs the algorithm to evolve the graph N steps.
|
Graph<V,E> |
get() |
int |
numIterations()
Retrieves the total number of steps elapsed.
|
protected int init_vertices
protected com.google.common.base.Supplier<V> vertexFactory
protected com.google.common.base.Supplier<E> edgeFactory
public BarabasiAlbertGenerator(com.google.common.base.Supplier<Graph<V,E>> graphFactory, com.google.common.base.Supplier<V> vertexFactory, com.google.common.base.Supplier<E> edgeFactory, int init_vertices, int numEdgesToAttach, int seed, Set<V> seedVertices)
graphFactory
- factory for graphs of the appropriate typevertexFactory
- factory for vertices of the appropriate typeedgeFactory
- factory for edges of the appropriate typeinit_vertices
- number of unconnected 'seed' vertices that the graph should start withnumEdgesToAttach
- the number of edges that should be attached from the
new vertex to pre-existing vertices at each time stepseed
- random number seedseedVertices
- storage for the seed vertices that this graph createspublic BarabasiAlbertGenerator(com.google.common.base.Supplier<Graph<V,E>> graphFactory, com.google.common.base.Supplier<V> vertexFactory, com.google.common.base.Supplier<E> edgeFactory, int init_vertices, int numEdgesToAttach, Set<V> seedVertices)
graphFactory
- factory for graphs of the appropriate typevertexFactory
- factory for vertices of the appropriate typeedgeFactory
- factory for edges of the appropriate typeinit_vertices
- number of vertices that the graph should start withnumEdgesToAttach
- the number of edges that should be attached from the
new vertex to pre-existing vertices at each time stepseedVertices
- storage for the seed vertices that this graph createspublic void evolveGraph(int numTimeSteps)
EvolvingGraphGenerator
evolveGraph
in interface EvolvingGraphGenerator<V,E>
numTimeSteps
- number of steps to iterate from the current statepublic int numIterations()
EvolvingGraphGenerator
numIterations
in interface EvolvingGraphGenerator<V,E>
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