Hi MFerrari!
First, let me thank you for your awesome mods! They're great!

So, I ran recently into performance problems on my current map, maybe you can help me.

Context:
- Warptorio playthrough (with your awesome! expansion + cold biters + explosive biters + alien biomes + ... ).
- Spawned on an 'island' with my ship (not to be confused with THE 'Island' preset!) that I cleaned up entirely from biters.
- Setup a (decent) factory outside
- Planet clock reached > 2000
- Started to notice slowdowns

At this point, I was suspecting this had something to do with warptorio surfaces (200+) not being correctly deleted, or maybe biters (not specificaly yours), because I knew I didn't expanded the factory enough to cause late-game slowdowns.

So I went in the editor, checked surfaces, and nothing to see here: current suface, nauvis, and ship floors. That's it.
So I checked biters then: reveal map, and noticed THAT:
https://imgur.com/tKMMyVu

There is 20+ of theses super-dense 'packs' of biters on my map!
(Notice that 99% of theses biters/spitters aren't attached to any spawner.)

1) Can you help me (and explain me why this is happening), please? xD
2) Can this happen in Vanilla too?

Thanks in advance for your time!

Hi. What surface is that? The current one ? Or nauvis. Can you check nauvis? That surface cant be deleted and causad this issue with me once. So i run a command on nauvis to killl all aliens. Problem solved. You can always run a command to kill all units. Not spawners. Should also solve these heavy packs

The surface on the screenshot is the current surface I'm on with the ship (warpsurf_231).

I checked Nauvis (by curiosity) earlier, and it's the first surface I ever started this playthough on.
Nauvis is pretty small and doesn't have a lot of biters/spawners. I ran away fast! xD

I know for the command but I would prefer to have a more permanent fix to this problem.
What's really strange to me is the amount of biters without spawner attached.
I suspect them to fight and set things on fire (maybe killing spawners?) and then establishing new bases/spawners, leading to this problem (ennemi expansion is on by default if I'm not mistaken).

An other pic:
https://imgur.com/a/DU8eznd

Evidence of them killing something:
https://imgur.com/YbbcAyJ

Little follow up:

So, I fixed my save by removing all the units with no spawner attached to them.
It cleared all the huge packs of biters we can see on the screenshots I posted earlier.

This is not The perfect solution (since I think it can remove some units which were legit without spawner) but oh well...
It does the job good enough for me.
I also removed all ennemies from nauvis thanks to your advice, since they are just eating ups for nothing.

Thanks again for your time!

good to know. I really have no idea why the pack this way...

I think I found what's going on.
When they die, your units damage the other units around them because the explosion you create at their position haven't their force properly set.

control.lua:
L56: ent.surface.create_entity{name=expl, position=ent.position, force}
L57: ent.surface.create_entity{name="explosive-biter-flame", position=ent.position, force}
L69: ent.surface.create_entity{name="small-atomic-explosion", position=ent.position, force}
L72: ent.surface.create_entity{name="small-atomic-explosion", position=ent.position, force}

should be:
L56: ent.surface.create_entity{name=expl, position=ent.position, force=force}
L57: ent.surface.create_entity{name="explosive-biter-flame", position=ent.position, force=force}
L69: ent.surface.create_entity{name="small-atomic-explosion", position=ent.position, force=force}
L72: ent.surface.create_entity{name="small-atomic-explosion", position=ent.position, force=force}

Same in Cold Biters.

Ohhh that might be the problem. I will fix those next update. Thanks

No problem! Glad to help!