shuffles g1 and g2 every time through the loop:

[jasonmastbaum]

I'm pretty sure the current player assignment loop will just always pop the same two players from any given pair of games. This shuffles the player list in g1 and g2 every pass through the loop as an additional step.

[UEWBot]

Looks like g1 and g2 are sets, not lists, so we can't shuffle them (in fact they don't have an ordering).
set.pop() apparently removes a random element.

[jasonmastbaum]

Ah. I ran a simple test of this looping through popping from a set and adding the popped element back and it looks like it's not exactly random, and just iterates through the elements of the set. But maybe for what we're doing that's close enough to random. I'd need to write more tests to try to figure out if the way _improve_fitness is set up, if every time it picks a given game, it'll start popping from the place it left off the last time it picked that game, or if it'll go back to the start of the sequence.

[jasonmastbaum]

If it does matter, I'm guessing it wouldn't be a big performance hit to make temp copies of g1 and g2 that are lists, do the sampling, then alter the sets if necessary, since it's just two seven-element lists on each iteration.