There's this theory that humans are antennas, and that we pick up "wavelengths from above" to build and create the world we live in. Not only did we decide on the same project name and idea, but we also used the same pre-processor hacks. How surreal.
As for your pqueue implementation, the efficacy of an optimizing compiler lies in the inherent complexity of the language. I can imagine the optimization backend for gcc is simpler (and more effective) than g++, but I am not an expert on compiler internals.
Its more likely that humans are redundant. That is, it is probable in a field of millions that two people come up with the same idea and implementation. I think the birthday paradox is a similar corollary on a smaller scale.
These kinds of macro hacks are pretty widespread, aren't they? To me, klib and its khash hash table is the most well-known implementation, see: https://github.com/attractivechaos/klib
And I've written similar things myself (hash table and vectors).
Where have you heard that theory? I've wondered about it myself, but other than some songwriter-specific conversation, I'm not sure I'm familiar with other people talking about it, and I'd like to be.
As for your pqueue implementation, the efficacy of an optimizing compiler lies in the inherent complexity of the language. I can imagine the optimization backend for gcc is simpler (and more effective) than g++, but I am not an expert on compiler internals.