Question about link_num in Generated Topology (HPN 7.0)

I have a question about the link_num in the generated HPN 7.0 topology. According to the generated topology file:

18 8 1 9 20 A100
8 9 10 11 12 13 14 15 16 17 
0 8 2400Gbps 0.000025ms 0
0 9 400Gbps 0.0005ms 0
1 8 2400Gbps 0.000025ms 0
1 10 400Gbps 0.0005ms 0
2 8 2400Gbps 0.000025ms 0
2 11 400Gbps 0.0005ms 0
3 8 2400Gbps 0.000025ms 0
3 12 400Gbps 0.0005ms 0
4 8 2400Gbps 0.000025ms 0
4 13 400Gbps 0.0005ms 0
5 8 2400Gbps 0.000025ms 0
5 14 400Gbps 0.0005ms 0
6 8 2400Gbps 0.000025ms 0
6 15 400Gbps 0.0005ms 0
7 8 2400Gbps 0.000025ms 0
7 16 400Gbps 0.0005ms 0
9 17 400Gbps 0.0005ms 0
10 17 400Gbps 0.0005ms 0
11 17 400Gbps 0.0005ms 0
12 17 400Gbps 0.0005ms 0
13 17 400Gbps 0.0005ms 0
14 17 400Gbps 0.0005ms 0
15 17 400Gbps 0.0005ms 0
16 17 400Gbps 0.0005ms 0

The file states that there are 20 links. However, based on the connection logic:

GPU to NVSwitch: There are 8 GPUs (0–7), each connected to one NVSwitch (node 8). This adds up to 8 links.
GPU to ASW: Each GPU (0–7) is also connected to an Aggregation Switch (ASW, nodes 9–16). This should also add 8 links.
ASW to PSW: Each ASW (nodes 9–16) is connected to the Pod Switch (PSW, node 17). This should add 8 links.

However, the topology file specifies only 20 links, which seems to leave out some connections. I may be misunderstanding the logic, so I’d appreciate clarification on the following points:

1.How is the link_num value of 20 calculated?
2.Are there specific links that are excluded in this count? If so, which ones and why?

Start by locating the HPN 7.0 topology-generation logic in the repository and compare its link-count calculation with the generated topology shown in this issue. Trace how GPU, NVSwitch, ASW, and PSW connections are counted; the work is done when the value 20 and any excluded links are clearly explained.