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ispd24: detailed route takes 2.5x longer for default groute compared to using 0.5 set_gloabl_route_layer_adjustment #5061
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It is hard to know a priori what the right amount of derate is, even for a routing developer. Finding a reasonable value is part of PDK setup today. The autotuner is helpful in this regard. Do you have a thought on how to do this differently? |
ispd19_test6 (detailed route contest) shows that the 'other' eda tools route guides wire length/via are very close to the achieved detailed routing. I'm don't know whether M1 was allowed "out of the box" or not. In order to get a similar results out of OR, one has to reduce the groute resources by 100% on M1 and by 50% on the other layers. Congrats to drt to be able to route violation free, considering the "bad" default global routing. But the runtime of 2:15 hours default vs 0:22 guides vs 0:26 reduced shows that groute defaults need tuning. I only have ispd19_test6 and ispd24 (nangate45) as datapoints. reading guides generated by 'other' eda tool
default groute M1-M9, 1.0 resources
groute M2-M9, 0.5 resources
|
Depending on the pdk's fill cells you might be able to do m1 routing in the unused sites. Most technologies benefit from some amount of derating but it is hard to make a general prediction. I'm surprised to see so little impact of derating on total wire length. I would think the increased derating would lead to increased detouring. |
Description
Testcase is ispd24 bsg_chip, Nangate45 tech.
The global router defaults are way too optimistic with regard to available routing resources.
This leads to 2.5x slower detailed route times compared to a run with only 0.5 the resources.
Default groute takes 23min whereas a run limiting the groute resources to 0.5 takes 9min.
It's a testimony to the quality of the detailed router to finish both runs without violations,
but one run needs 10 iterations, the other just 4.
This is even worse when allowing metal1 to be global routed.
The resource limited run creates slightly longer wires, but uses lot less via.
Suggested Solution
It would be good to adjust the default groute routing resource calculation to better correlate with what detailed_route can route.
Additional Context
ispd24 download
https://drive.google.com/drive/folders/1ocChoQupNxlLBH2hgqkPwR0-7D3ocTwm
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