前一段研读how google finds your needle in the web's haystack时，看到这幅图：
然后就冒出了用Graphviz把它绘制出来的想法，折腾了一下，结果接近：
这是源码：
digraph {
graph [
label="example 1",
//ratio=auto
];
node [
shape=circle,
style=filled,
fillcolor="#FBB5B8"
];
edge [
arrowsize=0.5
];
{ rank=same; 1; 3; 5; 7; }
{ rank=same; 2; 4; 6; 8; }
1->2;
1->3;
2->4;
3->2;
3->5;
4->2;
4->6;
4->5;
5->6;
5->7;
5->8;
6->8;
7->1;
7->5;
7->8;
8->6;
8->7;
}
Technorati : Graphviz, fillcolor, rank