On this infinite grid of ideal one-ohm resistors, what’s the equivalent resistance between the two marked nodes?

Even my grandma knows the answer to this one when all the resistors are the same. But what if they are not?

No need to say much about the classical ASTM D638 tensile test specimens AKA dogbones. Just a few remarks:

This post is about some finite element method code that I wrote back in 2014. I am sharing it here, even though I never finished the data visualization part I wanted back then