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#openlane
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# openlane
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Tayyeb Mahmood

05/22/2021, 2:28 PM
Hi All, I get following placement from the default hardening script of user_proj_example. Can an expert guide me how to relax this placement such that cells are more sparse. This design is too difficult to route.
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Hieu Bui

05/22/2021, 3:25 PM
I have had the same issue with the default script. You can try to disable PL_BASIC_PLACEMENT, enable PL_ROUTABILITY_DRIVEN and different values of PL_TARGET_DENSITY.
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Matt Venn

05/23/2021, 7:18 AM
I'd be concerned that your tools are not installed correctly. The example project script should work with no errors.
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Tayyeb Mahmood

05/23/2021, 7:27 AM
It is no error, instead the placement is beautiful. Only it is too congested to be routed. I was looking for a method that can make this placement more sparse, to help routing.
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Matt Venn

05/23/2021, 7:27 AM
If it's too congested to be routed, then isn't that an error?
Whe you run make user_proj_example and then make user_project_wrapper, do you get a clean result?
No DRC no lvs
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Tayyeb Mahmood

05/23/2021, 7:31 AM
This screenshot is of a modified user_prog_example build. I am unable to route it in reasonable time. Consider this as one of the design to be hardened as in your multi project example.
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Matt Venn

05/23/2021, 7:33 AM
So above when you say it's the default, that's not true?
Not trying to be snarky but you should try to be as clear as possible when asking for help. O
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Tayyeb Mahmood

05/23/2021, 7:36 AM
Sorry I meant default configuration script, config.tcl
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Matt Venn

05/23/2021, 7:38 AM
yeah, no problem. But there are lots of issues that can be side products of a tool install gone wrong, and then it wastes everyone's time trying to work out what the issue is when it's that the tools are bad
so a default run with user_proj_example should always work otherwise there is something badly wrong
so back to your q
try decreasing
PL_TARGET_DENSITY
(default is 0.55)
Or increase
CELL_PAD
default is 4
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Tayyeb Mahmood

05/23/2021, 7:43 AM
Tried first option, it yields a tiny island of cells in a big ocean placement remains same.
Let's try cell_pad
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Matt Venn

05/23/2021, 7:45 AM
Also, I've had success with @Hieu Bui’s suggestion of PL_BASIC_PLACEMENT
also, try decreasing FP_CORE_UTIL (only has effect if your die size is not absolute)
I would put a bunch of these into a configuration script and use run_designs to try all combos
then check the resulting spreadsheet to guide you
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Tayyeb Mahmood

05/23/2021, 9:44 AM
Apparently, turning off PL_BASIC_PLACEMENT was the best option, and there is good reason to do so. I will write in detail to help others on this forum but for now thanks a lot @Hieu Bui and @Matt Venn
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