It's the slowest mod I've tried, usually taking between 0.300-0.500 per frame. I tried disabling most of the options, but it didn't seem to improve performance. Which is sad, because this mod sounds like it's exactly what I need!

Is this a megabase save? Do you have lots of attacks happening? What are mods are you running?

Otherwise there isn't much I can do for you, if I knew a way to make it much faster and retain the functionality I would do it. This comes down to the implementation method I've chosen and the limits of the current factorio engine.

Unfortunately you may need to wait til 0.17 for the performance improvements and api changes it brings.

Not a megabase, this is with new games. I was playing Sandbox, and no attacks were happening.

Are you using other mods?

I am using some other mods, which I'll list below. I was trying Rampant version 0.16.33, in case that's relevant.

These may have been interacting with Rampant:
Nightfall_0.16.3
rso-mod_3.8.1

I doubt any of these mattered:
AsphaltRoads_1.1.3.zip
auto-research_4.2.0.zip
beautiful_bridge_railway_0.1.3
combat-bot-booster_0.16.1
Dectorio_0.8.9
Dirt_Path_1.1.41
dirty_power_0.1.0
extinguisher_0.16.0
Flammable_Oils_0.2.0
Nuclear Landmines_1.0.0
Orbital Ion Cannon_1.6.3
PavementDriveAssist_2.1.6
ProgressiveRunning_1.0.16
ScanningRadar_0.2.9
scattergun_turret_3.7.0
searching-flashlightR_1.3.0
Vehicle Wagon_1.2.5

Non-Game-Changing:
BorderedAlertIcons_1.0.0
bullet-trails_0.3.1
Laser_Beam_Turrets_0.2.0
minime_0.0.6
MushroomCloud_1.0.3
MyPlayerColor_1.0.1
SlightlyBetterSounds_0.16.2
SmallRobots_0.0.1
UsefulMapColors_1.1.10

Since I had just started a new game, there wasn't any mod content in play. Likewise, I had no trains, electricity, logistic network, etc. going on, and I hadn't attacked, made pollution, put up turrets, or otherwise provoked the aliens.

if you load just rampant what are the times like?

I just tried it. Still averaging 0.200-0.400 per frame. Here's a screenshot:
https://i.postimg.cc/BvzHWxQ5/Screenshot_2018-10-04_14-31-27.png

I average around 0.200-0.300.

Ideally, for a game supposed to be running at 60 FPS, you'd want to cut that down to 0.015 or lower. Are there any calculations which don't NEED to be run every frame (particularly anything iterating over many entities or tiles) which you could possibly do once every 5 or 10 frames, or that you could memoize instead of recalculating?

I was under the impression the numbers in the debug console were milliseconds.microseconds
as the frame cycle hovers around 16.67 which is the 60 fps you are talking about. So I believe the 200-300 is in microseconds and not milliseconds.

In the screen shot you posted the game render cycle is taking 39 milliseconds which Rampant has nothing to do with.

I do a great deal of value memorizing and subdividing long running tasks over many ticks.

The code is open source and I welcome you to take a look to aid in optimizing the code base. I feel like it has been optimized fairly well for being in lua, but am open to better solutions or clever tricks.