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Voyager
14,904 Views
Registered: ‎06-19-2014

What is "Number of Nodes with overlaps" parameter in implementation?

During routing of my design in vivado , i get a parameter in log report that is Number of Nodes with overlaps = some value

- Can someone tell what is this?

- What should be a nominal approx value of this parameter?

- If it has a high value like 20-30k, what will be impact on implementation?

1 Solution

Accepted Solutions
Voyager
19,490 Views
Registered: ‎06-19-2014

I found that the problem was in clock planniing. Implementation was taking veryyyyyyy long because i had used a regional buffer to clock my much tangled and large set of logic. Routing tool was taking too long because it was trying to route logic in one region.

I used BUFMRCE and then BUFR so that logic can take clock from adjacent regions also.

Now implementation time is reduced to around 50 minutes, from 7 hours.

Tags (1)
10 Replies
Scholar
14,898 Views
Registered: ‎06-14-2012

node overlaps means that you have multiple nets fighting for the same routing resource. If that number is high, this indicates some overall congestion problem, and there may be further clues in the Placer log.

If you have the placed checkpoint, you can view the congestion map (estimated based on placement) from Window -> Metrics -> Vertical/Horizontal routing congestion. That may indicate which regions are giving problems and it may help develop a floorplan.

Hope this helps.

Regards

Sikta

Voyager
14,889 Views
Registered: ‎06-19-2014

During routing i get in log file

Phase 4.2 Global Iteration 1
Number of Nodes with overlaps = 20013
Number of Nodes with overlaps = 7137
Number of Nodes with overlaps = 4033
Number of Nodes with overlaps = 2505
Number of Nodes with overlaps = 1144

Phase 4.3 Global Iteration 2
Number of Nodes with overlaps = 8172
Number of Nodes with overlaps = 1588
Number of Nodes with overlaps = 349
Number of Nodes with overlaps = 105
Number of Nodes with overlaps = 33
Number of Nodes with overlaps = 16
Number of Nodes with overlaps = 10
Number of Nodes with overlaps = 1
Number of Nodes with overlaps = 1
Number of Nodes with overlaps = 0

As you can see that the router eventually solves problem with overlapping nodes but it takes it around 6 hours to do so.

Does floorplanning help minimize initial figure of  "Number of Nodes with overlaps = 20013" ?

Scholar
14,887 Views
Registered: ‎06-14-2012

Please analyse the congestion metrics as listed in the earlier post and then floorplan the area where you see congestion numbers to be high.

Floorplanning definitely helps in reducing congestion.

Regards

Sikta

Voyager
14,867 Views
Registered: ‎06-19-2014

Hi Sikta,

i am attaching the device view which is showing where is the congestion in horizontal routing (the pink area).

Now what's next? how to floorplan to remove this congestion? any document?

Voyager
14,839 Views
Registered: ‎06-19-2014

my problem is not solved yet

Voyager
19,491 Views
Registered: ‎06-19-2014

I found that the problem was in clock planniing. Implementation was taking veryyyyyyy long because i had used a regional buffer to clock my much tangled and large set of logic. Routing tool was taking too long because it was trying to route logic in one region.

I used BUFMRCE and then BUFR so that logic can take clock from adjacent regions also.

Now implementation time is reduced to around 50 minutes, from 7 hours.

Tags (1)
Contributor
5,501 Views
Registered: ‎07-03-2018
Hello @Anonymous,

How do you change BUFMRCE and BUFR?

Because as normally, I just assigned clock to pin in constrain file (.xdc), I don't know how to check clock buffer I'm using and how to change it as your solution?

Thank you,
Yuri
Voyager
5,476 Views
Registered: ‎06-19-2014

Read "Use Cases" on page 105 of ug472. It will give you idea of how to use BUFMRCE and BUFR.