I am making a graph using dot that splits into 4 parallel rows with links between them (see code below). I have organised the starting nodes into a subgraph using rank=same to ensure they start in line vertically, and then used edge[weight] to ensure each row is a straight horizontal line.

Due to the links between the rows, the initial nodes are unequally spaced vertically. Is there a way of setting them to be equal distance (i.e. increasing the distance between rows C,D,E to match the distance between B,C)? I have tried using nodesep in the subgraph but there is no effect. Any ideas?

graph Example {

rankdir=LR
ordering=out

{ rank=same
b1
c1
d1
e1
}

a1--b1
a1--c1
a1--a2--d1
a2--e1

edge[weight=100]

b1--b2--b3--b4
c1--c2--c3--c4
d1--d2--d3--d4
e1--e2--e3--e4

edge[weight=1]
b1--bc--c3

}