[graph-tool] How can i set minimun distance between nodes (so they do not overlap each other)

I am using sfdp_layout. How can i modify it so nodes do not overlap each other alot and can show edges? Graph going to be huge (Millon of nodes) so what is best algorithm for it ? below is my result and code of 70k nodes (email conversation) : <https://lh3.googleusercontent.com/-mp9AYfKCLN8/U0WHfv93LiI/AAAAAAAAAvE/46g3j4OQHBc/s1600/test_p10.png>

def draw_graph(userdict,edges): g = Graph() g.add_vertex(len(userdict)) for edg in edges: g.add_edge(*edg)

#pos = sfdp_layout(g, C=0.8 , K=4, cooling_step=0.69) pos = sfdp_layout(g,p=10, cooling_step=0.69) for vertex in g.vertices(): print pos[vertex] return g

Thanks Phyo.