cluster.gv

digraph G {
	subgraph cluster_0 {
		node [color=white style=filled]
		style=filled
		color=lightgrey
		a0 -> a1
		a1 -> a2
		a2 -> a3
		label="process #1"
	}
	subgraph cluster_1 {
		node [style=filled]
		b0 -> b1
		b1 -> b2
		b2 -> b3
		label="process #2"
		color=blue
	}
	start -> a0
	start -> b0
	a1 -> b3
	b2 -> a3
	a3 -> a0
	a3 -> end
	b3 -> end
	start [shape=Mdiamond]
	end [shape=Msquare]
}