You're right, my version is unoptimized because I was trying to keep the code neat as in the article. I think that optimizing the code for hypothetical future r

You're right, my version is unoptimized because I was trying to keep the code neat as in the article. I think that optimizing the code for hypothetical future reuse is a bit premature. You could make a performance argument, but this optimization is going to prevent just 2 memory accesses, which aren't going to matter much compared to all the rest. If I was chasing performance I would start by memset'ing the top and bottom edges since they're contiguous in memory.