@User remember we were talking about adding that tiny inverter design to the examples?

https://github.com/efabless/openlane/tree/develop/designs/digital_pll_sky130_fd_sc_hd However, unlike the digital_pll the issue here is that the design is too small. So maybe try using an absolute FP_sizing and skipping initial placement but this feature is not yet in master. An example configuration of a tiny design that doesn't have a clock looks like this:

set ::env(RUN_SIMPLE_CTS) 0
set ::env(CLOCK_TREE_SYNTH) 0
set ::env(FP_SIZING) absolute
set ::env(DIE_AREA) "0 0 160 160"
set ::env(PL_TARGET_DENSITY) 0.20
set ::env(SYNTH_MAX_FANOUT) 6
set ::env(PL_SKIP_INITIAL_PLACEMENT) 1

set ::env(FP_PDN_VOFFSET) 4
set ::env(FP_PDN_VPITCH) 6
set ::env(FP_PDN_HOFFSET) 0
set ::env(FP_PDN_HPITCH) 9

We're conducting some final tests and rc3 will be coming over the weekend. So, then you'll be able to use

PL_SKIP_INITIAL_PLACEMENT

great

develop

ok!

Hi @Matt Venn, try adding the following lines in your config:

set ::env(CLOCK_PERIOD) 0
set ::env(CLOCK_TREE_SYNTH) 0

ok that's moved me on a bit

try out absolute sizing, it wouldn't make a difference for the floorplanner but it does for the global placer. example:

set ::env(FP_SIZING) absolute
set ::env(DIE_AREA) "0 0 160 160"
set ::env(PL_TARGET_DENSITY) 0.20
set ::env(PL_SKIP_INITIAL_PLACEMENT) 1

Also, try removing:

set ::env(FP_PDN_VOFFSET) 15
set ::env(FP_PDN_VPITCH) 5
set ::env(FP_PDN_HOFFSET) 15 
set ::env(FP_PDN_HPITCH) 5

The configurations should self adjust for the pdn in rc3 (hopefully to the correct values)

that brings the failure back to the replace

small designs can be tricky to configure, but running an exploration should speed up the process

ok,

So far, fixing an absolute size with low density and manipulating pdn configurations seemed to work for me pretty well. But, I've never tried a design composed of one standard cell. Still, it would be a good starting point.

ok, I'll give it a go thanks

@Matt Venn: I can't help but wonder why you're trying to harden a design with only one cell?:)

because I think it will be useful to help complete beginners how this stuff works

Got it; useful for educational reasons for sure 👍

OK I'm a bit confused

I would try increasingly lower and lower core utilizations and placement densities.

ok that would be great

this is one example of a configuration file. The generated configurations are actually appended to the config.tcl (for each run).

the docs say "all possible combinations of the passed regression file"

maybe try writing a config file: densUtil.config

FP_CORE_UTIL=(25 50 60)
PL_TARGET_DENSITY=(0.5 0.6)

and run

python3 run_designs.py -d spm -t testExploration -th 6 -r densUtil.config

pointing to the densUtil.config This should clear up what the script does, you'll find a couple of configuration files generated under spm and 6 runs will be started.

thanks. So the stuff in brackets are the combinations to check

Yes

ok yes thanks now I get it

can you change that to a PR to develop?

done

Thanks!

anyway to find out how the combinations went? It looks like there is some tool that tries to run after but it seems very broken

after their completion you'll find a summary generated under the regression_results folder. Check this.

thanks

@Matt Venn: I would try

FP_CORE_UTIL=(0.1 0.5 1 2 3 4 5)

as well.

ok thanks

@Matt Venn: I'll try out your design as soon as I can (probably early tomorrow). Thank you very much for bringing this up! and definitely once we find the proper configurations, it would be a huge help to PR this to develop.

Thanks! Very happy to contribute when I can.