Is there any way I can avoid death by FPS in Dwarf Fortress?

So uh... my fort at the moment has around 106 dwarves/petitioned entertainers and 20 visitors. The problem is (and this occurred suddenly) is that the FPS has been reduced to ~4 FPS. This is unplayable for me. Is there any way I can restore the FPS back to at least 20?

Most of this advice comes from the wiki page on improving framerate. Some of it unfortunately requires pre-action, before your current point.

A number of things can impact framerate. Flowing water for example takes a lot of CPU power. Item count can affect it, though number of squares with items in them affects it more. Pathfinding can cause trouble.

I find that creature count is my biggest offender, but I don't generally have large amounts of flowing liquid in my forts.

However changing the structure of your fort with framerates that low is going to be a pain and a half. There are some things you can turn off in configuration files that may help. The important file here is df/data/init/d_init.txt. In this file you can adjust things like the population cap which would let you avoid having too many dwarves in the first place. You can also turn off temperature calculations which can speed up the game some.

Not knowing a huge amount about your setup, I would recommend turning off temperature, at least temporarily, to get enough speed to work with. Be sure to also reduce your population cap. Otherwise your population will just keep growing and slow you back down again.

I would also confine all your animals to walled off pastures or cages and close off unneeded areas to reduce pathfinding slowdowns. If you have any waterfalls or pumped areas, turning them off could also help.

Some people don't like to use what feels like a bug, but quantum stockpiles can help. Geting all the random junk consolidated is supposed to help framerate.

If some of the random items are things you will never want, like XXPig tail sockXX, You can use a Dwarven Atom Smasher to remove them from the game and no longer spend any CPU cycles at all tracking them. This however is going to be a minor improvement at best, unless you have tens of thousands of worn out socks.

Look at the framerate wiki page and see if any of its other ideas apply in your situation.

Some things can be done:

• Shut off that dwarven reactor and any sources of moving water
• Only female animals are useful. Slaughter everything but the females and maybe 1-2 males for breeding
• For chicks, build a grid of 1x1-rooms with a nest in it, seal each of them with a door
• For anything grazing, build similar structures, albeit a bit larger. Size depends on creature type unfortunately. Of course, these animals need food and cannot graze inside.
• Build a dwarven atom smasher and get rid of the junk lying around
• Make sure that you only dig small corridors, 1 - max 3 spaces wide (and 3 only where there is loads of traffic). Wall off large, unused parts, for example where you mined out for resources. Use the traffic designators, use forbidden for parts that need no maintenance. Use burrows. If your miners only need access to lower levels, restrict them to that. Make burrows as small as possible.

In my experience, the last point has the most significant effect, since the pathfinding needs a lot of CPU time and it will not consider spaces not reachable or outside of the burrows. The key point here is to restrict creatures as much as possible.

And never, ever, embark in a coastal biome. The waves are nice and stuff but you will have died the FPS death even before you arrived.