Matt Aamold12/01/2020, 3:52 AM
script erroring out. When I implement my design at the
level, and run
on it from the
directory, I'm still getting several
messages followed by
Warning: detailed placement failed on _44889_
followed by the
Warning: Overlap check failed (136).
fatally erroring out. Are the openlane devs aware of this or should I open an issue on github? Or am I doing something incorrect here?
aryap12/01/2020, 6:00 AM
) will actually work. it takes a bit of guesswork but with some hair pulling it will work.
Matt Aamold12/01/2020, 1:02 PM
Amr Gouhar12/01/2020, 4:55 PM
. Specially the last two.
Here is a note I added to the caravel repo and will be included in the release notes when rc5 is out.
NOTE: rc5 (current openlane develop) and rc4 (current openlane master) are using two different concepts of cell padding. rc4 is modifying the LEF, while rc5 is relying on openroad to handle the cell padding. Also, rc4 is using the standalone version of openDP while rc5 is using the one integrated in the openroad app. This affects the concept of PL_TARGET_DENSITY and while in rc4 it was preferred to have PL_TARGET_DENSITY=(FP_CORE_UTIL-(5~10)/100). Now, in rc5 it is preferred to be PL_TARGET_DENSITY=(FP_CORE_UTIL+(1~5)/100). FP_CORE_UTIL should be relaxed as well as it became more representative of the actual core utilization, which wasn't so much the case earlier. So, the perception of these two variables as well as CELL_PAD changed between rc4 and rc5 which necessitates a change in the configurations of almost every single design. CELL_PAD should be 4~6 for the skywater libraries in rc5 unlike rc4 which was 8.This will be included in the release notes when rc5 is released as well as the openlane wiki.
Matt Aamold12/01/2020, 5:45 PM
with a value of
, but I wasn't specifying either
. I've been able to get past the fatal error from
. I'm getting a fatal error during fastroute now, but I'll leave that as a different thread. I'd like to understand what the deficiency was when not specifying
(i.e., what their default values were) so I can tune these values better. Are there "typical" values for
Amr Gouhar12/01/2020, 5:56 PM
is std_cell specific thing to keep a space around the cell to easily access the pins while routing (so the higher the
the less the actual utilization). Typically for rc5/develop
for the skywater libraries should be 4~6. I think you might find this useful as well.
Most of the time the solution to all congestion and failed placement errors is to reduce the
and then change
to reflect that.
https://github.com/efabless/openlane/blob/develop/regression_results/benchmark_results/SW_HD.csv This sheet, should give you a sense of what to set FP_CORE_UTIL and PL_TARGET_DENSITY for a specific design based on its proximity in the cell count to any of these 40 designs.