example: density sweep

[oharboe]

@jeffng-or @maliberty @luarss FYI

For MegaBoom, the build times are ca. 12-24 hours, so "sweeps" of parameters will have to be planned manually.

I'm wary of trying a million parameters with a credit card and an automatic cloud solution :-)

Bazel "property sweep at home"... "at home" here as in a mom telling the kids that "We have burgers at home" when passing by a burger resturant... Of course the "burgers at home" are not nearly as nice as that fancy burger resturant... But, it gets the job done. :-)

These tests are run in parallel:

• the build is only re-run from the stage where the property has never been built. Since PLACE_DENSITY affects floorplan, builds are rerun from floorplan. To save CPU, it is possible to "cheat" and only rerun place with a new density to speed things up and have a shared PLACE_DENSITY for floorplan and do a sweep based on that in place. One might learn something that way and redo a narrower sweep with all stages?
• runs all the tests in parallel
• artifacts are produced so they can be downloaded and inspected if the build happens on a server

In this simply example, I'm only after a go/no go, but for other properties it might be interesting to run some scripts to examine the different results.

Very similiar, but not quite identical results...