open-source-silicon.dev

I was just looking at PL_DIAMOND_SEARCH_HEIGHT was removed as a parameter. This was previously needed to allow legalization with big macros. The comments say that the new default is "height*5", is that the height  of the biggest macro or a standard cell? If it's a cell, this is a big problem.
<@U020J2W6Q84>

It seems that this was observed as a problem back in August when it was removed:
<https://skywater-pdk.slack.com/archives/C016H8WJMBR/p1629299836114100>

<@U020J2W6Q84> what do you mean? I linked the prior message above as well as my issue at the top of this thread.

&gt;  The comments say that the new default is "height*5",
Where is that stated? The commit description?

<https://github.com/The-OpenROAD-Project/OpenLane/blob/master/configuration/README.md>

```Removed: Specifies the diamond search height used for legalizing the cells during detailed placement. The search width is calculated internally as heigh*5. For designs that contain big macros, increasing this value to above 400 will allow for more search space and more potentail for successful legalization.```

It's removed, so I wouldn't count on this documentation for much other than knowing that it's removed. I would open an issue against OpenROAD.

I get a lot of errors with legalization and overlapping cells. I'm assuming it is because of this.

<@U018LA3KZCJ> Do you know whether this would be an issue in OpenRoad?

It was passed on to OpenROAD previously, but the OpenROAD app officially never exposed the diamond search height variable. When it stopped working, we removed it. If we were to re-add it, it would need to be exposed in OpenROAD first. OpenDP specifically.

I’m adding `detailed_placement -max_displacement 2000` in *scripts/openroad/or_opendp.tcl* to fix the overlapping (near macros) issue

<@U020J2W6Q84> This option is really needed for P&amp;R with macros. It used to exist back in v0.17 of openlane:
detailed_placement -diamond_search_height $::env(PL_DIAMOND_SEARCH_HEIGHT)
(in scripts/openroad/or_opendp.tcl). Otherwise, antennas and filler overlapping macros cannot be fixed.

I'm not disagreeing, but you'd have to make the case upstream to <https://github.com/The-OpenROAD-Project/OpenROAD/issues>. Once the variable is properly surfaced there, I'd be happy to pass it along.

Just something along the lines of a customizable diamond search height for OpenDP.

I don't see how anyone can complete a design with macros without this...

I can confirm that hacking it back in and using diodes+filler works now.