@Amro Tork (@Marwan Abbas, @jeffdi, @Andrew Wright): The 45 degree rules in the klayout DRC deck for gf180mcu are also wrong:

comp.edges.without_angle(0).without_angle(45).without_angle(90)
      .without_angle(-45).output('comp_angle',
                                 'ACUTE :  non 45 degree angle comp')

"ACUTE" means an angle of less than 90 degrees, and this is explicitly called out in the GF DRC documentation for "Polygon shapes to be avoided". No circles (roundflashes), no angles or inside corners on transistor gates, and no acute angles on diffusion, poly, or metal. The rule as implemented in the klayout deck prohibits any angle other than multiples of 45 degrees. That is not the definition of "acute". Generally speaking, acute angle rules are satisfied by spacing rules, given the way basic spacing rules are usually implemented. The caravel logo on GF may not have been intended to have non-45-degree angles on polygons (apparently they are an artifact of rescaling the logo from sky130), but they are not DRC errors.

@Tim Edwards I have to disagree with you on this. The geometrical rules are designed to check for angles of edges in the layout regardless of their relative angles to other edges. This rule makes sure that we don’t have any edges that are not 45 degrees relative to the layout plan. As for the “ACUTE” angle check for relative edges, that is normally part of the basic spacing/internal checks and it’s not part of the geometrical checks. I believe the implementation is correct for the rule. As for the logo design edges’ angles, I believe they are true violations due to some form of sizing as you mentioned.

The readthedocs statement of the rule differs from the GF documentation, and I think the rule was incorrected rewritten for readthedocs. The original GF documentation says:

SH.2: Avoid any COMP, poly and metal shapes with acute angles (angles <90 degrees). Exceptions are only for pre-tested metal inductors with IND_MK mark layers and lettering (non circuit elements).

Interestingly, they actually allow acute angles in alphabetic characters but (as far as I've found) give no layer to specify areas to be excepted from rule SH.2.

@Tim Edwards Geometrical checks are not considered guidelines usually also the foundry might refer to them in the document as guidelines. But those are what is considered as basic requirements for layers.

Please stop contradicting me. I am quoting the GF documentation verbatim.

I'm not trying to contradict you. I'm discuss those are required rules. I would appreciate if we could take this offline.