algorithm - is igraph preferential attachment directed graph acyclic? -

algorithm - is igraph preferential attachment directed graph acyclic? -

i generating graphs using barabasi-albert model implemented igraph:

graph.barabasi(10,5,directed=true)

how can sure generated directed graphs acyclic? there basic property implies that?

i found here model in question:

"this model lacks several properties of www : • if regard model producing directed network, generates acyclic graphs poor representation of web."

but how can sure of properties on graphs generated igraph?

the algorithm generates random scale-free networks.

here description of how works wikipedia:

the network begins initial network of m0 nodes. [...] new nodes added network 1 @ time. each new node connected m existing nodes probability proportional number of links existing nodes have.

this means if start out little acyclic network , add together new nodes directed edges point @ existing nodes. there no possibility of completing cycle in way since require existing node point new node.

when each new node connects 1 other node easy see resulting graph acyclic figure on wikipedia page shows. graph generated m = 1.

but property holds larger values of m when added edges directed.

note: assumed here seed-graph acyclic. if have had cycle in little seed-graph cycle of course of study remain new nodes generated , graph grows.

algorithm graph igraph directed-acyclic-graphs directed-graph