check the manual for createPlaceBlockage
these options you mention help you to cover some macro with a placement screen. the ring options are like an offset that can be applied to every edge or side. I agree that ring is not a good name, but it is what it is.
Thank you so much for your response. However, I still have some trouble with visualizing it in my mind, because I don't understand how it works when both "inner_ring_by side" and "outer_ring_by _side" are specified, like this:
create_place_blockage -hinst something -inner_ring_by_side {10 10 10 10} -outer_ring_by_side {5 5 5 5}
Let us assume hinst named something has an initial shape {llx, lly, urx, ury = 100 100 200 200}. When applying inner_ring_by_side to it , it shrinks to {llx, lly, urx, ury = 110 110 190 190}
, but when applying outer_ring_by_side to it, it then grows to {llx, lly, urx, ury = 105 105 195 195}.
I am new to placement. So when people say "to apply a blockage on an hinst", what does it really mean? To my understanding, the blockage was first put there, and then placer needs to put instances somewhere else to avoid this region, but this "inner/outer ring offset" thing really confused me, because it sound like "You first have instances put somewhere, and then your blockage shape will be calculated from the instances coordinate and inner/outer ring offsets".