How to investigate global routing problems

[oharboe]

I seem to recall there was a feature that included the nets that were involved in the congestion under the DRC?

I was testing out #1333 on sky130hd/microwatt because it is the only design that has hard global routing in the ORFS repository.

mpl2 doesn't solve the global routing issue in sky130hd/microwatt, not that I know if it can...

diff --git a/flow/designs/sky130hd/microwatt/config.mk b/flow/designs/sky130hd/microwatt/config.mk
index 4b4eb79d..33d5812d 100644
--- a/flow/designs/sky130hd/microwatt/config.mk
+++ b/flow/designs/sky130hd/microwatt/config.mk
@@ -31,4 +31,5 @@ export CTS_CLUSTER_SIZE = 30
 
 export export SETUP_SLACK_MARGIN = 0.2
 
-export GLOBAL_ROUTE_ARGS=-congestion_iterations 100 -verbose
+export SYNTH_HIERARCHICAL = 1
+export RTLMP_FLOW = True

global routing DRC report after 20 iterations:

[vijayank88]

@oharboe
With the hierarchical synthesis have you checked its placement/routing heat map?
Because it's implemented for flat design with fixed die size.

[oharboe]

Placement heatmap:

Routing congestion heatmap:

[oharboe]

@oharboe With the hierarchical synthesis have you checked its placement/routing heat map?

Above.

Because it's implemented for flat design with fixed die size.

Why is a fixed die-size required?

[vijayank88]

Yes, I understand your requirement. It's similar to my request already raised: #1216

Because during congestion, flow get terminated without writing current stage .odb file.
Even though we have congestion.rpt it can't be located with OpenROAD gui.
Only if we run with test case, we can able to trace those nets with x marker in GUI.

To view congestion report we need global routing stage database not cts stage .odb.
Hope I've cleared your issue on why congestion marker not show as per the steps you followed.

[oharboe]

Actually, the net information should be saved in the .rpt file, the .odb file doesn't enter into it, as I understand.

From https://github.com/The-OpenROAD-Project/OpenROAD/blob/36bd481ac8a9edf401ba5e5b6bb0c379ac958467/src/grt/src/fastroute/src/utility.cpp#L2367
, that's global routing, we see that it saves net information, if there is any.

This leads to the next question: why isn't there any net information in this case?

[oharboe]

@maliberty Should there be any net information in this case, looks like there should have been reading the source code?

[maliberty]

There should be so open an issue if needed

[oharboe]

Done: The-OpenROAD-Project/OpenROAD#3867