Code A113

I was thinking about this at work, explaining it to one of the students I work with. He had never seen Wall-E, so I explained it in a generic and non-spoilery way. Since no one but me reads this anyway, I am going to write it the spoilery way here. You have been warned.

In that story, the systems on Axiom are programmed to look for habitability on Earth, and when it is proven, the ship is to return to Earth. It's an interesting but very expensive backup for just a normal recall message.

So, the pseudocode looks something like this:

while in_space do begin
  if(check_earth_habitability()) {
    return_to_earth();
  }
  sleep(1 year);
end

The function check_earth_habitability() is incredibly expensive to evaluate, as it involves sending a spacecraft with several EVE probes all the way back to Earth. It's like us making an implementation of go_to_saturn().

Directive A113 instructed the autopilot to not return to Earth under any conditions. It could have been implemented by cancelling the entire loop (including never sending EVE back to Earth), but instead the implementation looks like this:


while in_space do begin
  if(check_earth_habitability()) {
    //return_to_earth();
  }
  sleep(1 year);
end

A normal person would ask "Why does Auto send Eve back to Earth year after year if it has been ordered to not return?" I ask a similar question "Why did they do the code that way?" The thing is, I have done things similar to this: Evaluate an incredibly expensive function, just to ignore almost all of its output.

An example from work is sim_sample. A lot of times I only care about a small part of the result of sim_sample, or I have already calculated the result and could just run viusalize_1c manually. I don't because it is easier to run sim_sample and wait for it to finish than it is to do it efficiently.