
Cities: Skylines Is Turing Complete - 0xdada
https://medium.com/@balidani/cities-skylines-is-turing-complete-e5ccf75d1c3a
======
sowbug
If anyone is looking to buy this game, it's currently on sale at Humble Bundle
for $7.50. [https://www.humblebundle.com/store/cities-
skylines](https://www.humblebundle.com/store/cities-skylines)

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folli
Any experience running it on Linux? Using Wine?

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helb
It runs on Linux natively. Works well for me (installed via Steam).

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onli
Same goes for all the extensions. The Linux version is really solid.

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Snuggle
The performance is a fraction of that on Windows though, from my experience.

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want2know
Might this be a memory issue? I run it on Xubuntu and noticed it sometimes
uses all my 8GB RAM so the PC starts swapping.

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jjwhitaker
It loves RAM (and probably RAM speed), but not necessarily in a bad way.
Jumping to 16gb (2x8gb) from 8gb (1x8gb) on the laptop I first played it on
was a big jump in performance even with a GT740.

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whatshisface
I think this has some meaning for the abundance of life in the multiverse. If
most human-created systems of sufficient complexity turn out to accidentally
support computation, then maybe most laws of physics support computation.

Hey, it's not better or worse than any other way to guess.

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bordercases
> Hey, it's not better or worse than any other way to guess.

Saying this is a kind of relativism that closes you off to receiving criticism
for this view.

Here is some disagreement from the philosopher of information Luciano Floridi,
"Against Digital Ontology": [http://philsci-
archive.pitt.edu/4076/1/ado.pdf](http://philsci-
archive.pitt.edu/4076/1/ado.pdf) and its sister paper "A Defence of
Informational Structural Realism":
[http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.135...](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.135.5500)

You might to be tempted to ignore this paper for being too technical, but it
would be technical only because these are real issues that become difficult
when put under serious reflection.

If you can stomach it you will be rewarded with deeper understanding.

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whatshisface
That's a paper about ontology, I'm talking about the actual physical reality
of "the multiverse," you know, the one with the meta-landscape of all possible
string theories, and all the different spidermans.

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bordercases
In what way can statements about a multiverse not be ontological? Are you
committing to modal realism, Platonic realism, or are you just pulling my leg?

If you commit to the multiverse being physical, by extension you're making
claims about ontological concerns, since all physical claims require there to
be a notion of something existing, even if you're wanting to claim that
something counterfactually exists. Then that gets into modal realism etc etc.

Likewise you can't be fully confident in multiversal theories since no
physicist endorses a multiversal theory without also accepting it as
interpretative, as no experiment has been performed to anoint multiversal
theories as being correct. So you're still postulating something worthy of
criticism even if there was nothing ontological involved.

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whatshisface
Each universe gets its own version of Spiderman, and we live in the universe
with the fictional Spiderman. That's one theory that matches our observations.
Since basically every theory matches our observations, including the theory
that there isn't a physical multiverse, every argument is equally specious and
aesthetic.

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bordercases
Every theory matches observations _given interpretations of those theories_ ,
and it's impossible to engage in discourse without additionally engaging in
interpretation. So some theories are going to be eliminated from view given
one perspective or the other since interpretations must be chosen over others.
I think where you're wrong is thinking it's possible to evade this and make
the claim that all arguments are specious without simultaneously gesturing
that you don't want to engage in the discourse anymore: it's a self-defeating
claim.

Notice that none of this prevents there from being a singular subject that we
can talk about, but there can still be substantial disagreement as to the
nature of the thing be discussed. If we are disputing whether or not there is
a multiverse I would just ask you, what are your grounds for accepting that we
occupy a multiverse and what brought you to do so?

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thegagne
He watched Spiderman, and it was cool.

~~~
bordercases
Oh fuck I forgot about that part.

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altmind
I remember that classic TDD (transport tycoon) was also turing-complete. You
can make logical gates there using trains and railroad signals.

Minecraft is not only turing complete, there are multiple complete projects of
calculators and microcontrollers done using red stone.

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zokier
Redstone is by design made for implementing logic, so it belongs to slightly
different category. Although I think Redstones introduction was prompted by
people building logic without it in the olden days.

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Macha
I think Redstone's inspiration was people building computers in Dwarf Fortress
with floodgates and pressure plates, rather than Minecraft specifically.

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munk-a
Dwarfputers are a wonderful tangent of their own, with a not-unlikely
possibility of flooding your entire computer with firey death in the form of
magma in some of the more impressive approaches - this has been possible (but
quite difficult) for some time, more recent game versions have made non-fluid
based logic gates[1] more realistic and usable.

Someone has built an (admittedly simple) space-invaders game[2] using df which
is rather impressive.

1\.
[http://dwarffortresswiki.org/index.php/DF2014:Computing#Disc...](http://dwarffortresswiki.org/index.php/DF2014:Computing#Disciplines)

2\.
[https://www.youtube.com/watch?v=j2cMHwo3nAU](https://www.youtube.com/watch?v=j2cMHwo3nAU)

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dnos
The idea of creating computers out of virtual objects has always fascinated me
since I first saw someone do it in Minecraft.

It really brings up some interesting scenarios that I like to day dream about
sometimes.

For instance, in a real world simulation, you could build a processor with a
gazillion transistors because you don’t have to worry about the same physical
limitations like size or heat. Could it take an input and compute an output
faster than something in the real world?

Would you be bound by the speed of light in the virtual world? You control the
physics in your virtual world, so technically nothing prevents it right?
Information can travel faster than the speed of light relative to your virtual
objects. Say you model the earth at 1:1 scale in the simulation and have
avatars on complete opposite sides of earth. They could exchange messages
faster than they could in the real world since the information wouldn’t have
to physically travel across physical space. (e.g. send message directly to
memory address X instead of sending light through fiber optic physics
simulator).

Essentially, in a simulation of the physical world that has tweaked physics,
could information be processed faster than the processor running the
simulation?

Is there some sort of conservation of energy law, but for information?

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bordercases
The information would "appear" to be processed "faster" to the digital system
merely because the digital system would have no memory of there being a moment
in between its current state and the next computed state. Even supposing that
it's possible for there to be a subjective experience of a computer: this goes
in to physical time and psychological time and whether the two bear a strict
relation, as well as the relative nature of time in physical space.

On the first topic, if you can stomach having to reformat a PDF, the "No Free
Lunch in Machine Learning" guy wrote a paper on thermodynamics and
psychological time:

[https://www.researchgate.net/publication/226069884_Memory_sy...](https://www.researchgate.net/publication/226069884_Memory_systems_computation_and_the_second_law_of_thermodynamics)

On the second one... I think it's more interesting to think if there's a
theory of relativity for computation. Imagine if two systems were updating one
another's state but were separated by physical distance. Wouldn't you have to
hold the state of one to only update when it a receives a message from the
other, for the systems to "experience" instantaneous communication? That would
mean there would be a third system for whom time would have to pass to
transfer the message and compute it in such a way that the amount of updating
required for the receiving systems are minimal.

Maybe we have to guarantee that at least one system has to experience time
more slowly than the others, to compute the information necessary for
instanaeity to be true for the communicating systems.

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helb
Somewhat related: turing complete (Open)TTD.

segment display: [https://www.tt-
forums.net/viewtopic.php?f=29&t=37902](https://www.tt-
forums.net/viewtopic.php?f=29&t=37902) (2008)

digital clock:
[https://www.youtube.com/watch?v=mkQBGJeh12U](https://www.youtube.com/watch?v=mkQBGJeh12U)
(2011)

binary adder: [https://www.youtube.com/watch?v=fwWo9fL-
GZs](https://www.youtube.com/watch?v=fwWo9fL-GZs) and
[https://www.youtube.com/watch?v=YyEzm1ghAsU](https://www.youtube.com/watch?v=YyEzm1ghAsU)
(2015)

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vzola
Am I the only one who didn't enjoy Cities: Skylines? I played without any
expansion (wasn't really hooked enough by the base game to go looking for
them) and found the gameplay quite limited compared to the few old city
building games I played as a kid. I still play Pharaoh to this day 20 years
later and it's still challenging and complex and there's tons of gameplay to
explore. In comparison, I played Cities: Skylines for about a weekend, got
over the initial difficulty with managing finances, and then it became a
matter of building pretty roads and forcefully read people's complaints on in-
game-Twitter.

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want2know
The game is most about traffic management. This is not very surprising because
the company behind it was focused on traffic games.

I like the game a lot. But to be fair: you must download a good traffic
control mod to setup traffic lights and road settings to keep the traffic
under control.

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ekiwi
Wouldn't you also need a way of storing information (preferably an unlimited
amount of information) for Skylines to be turing complete? How would you
implement the tape of the turing machine?

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davrosthedalek
You can make memory out of logic gates.

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zokier
Adders belong to category of combinational logic, which by definition excludes
memory. So OP is right, they do not yet demonstrate Turing Completeness. I
imagine, but don't actually know, that they would be about as expressive as
dfa, which are few steps below turing machines

~~~
davrosthedalek
He builds the adders from ANDs, ORs and NOTs. With these, you can also build
flip-flops, which are memory. (Actually, it's enough to have only NAND (or
NOR) to build all logic circuits, including memory)

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hcnews
Trying to understand the excitement around this. Is it uncommon for games to
be turing complete? I imagine a lot of modern games are complex enough to pass
turing completeness check.

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bduerst
It's more or less an feat in problem solving. Given a specific set of
limitations in simulation, can you recreate and solve this computation
problem?

For some games, like Minecraft (redstone) and Factorio (logic gates) it's
easy, but for others it's difficult enough that you get to see some
creativity. This is one of those latter instances.

~~~
desmondw
Interestingly, Minecraft only added redstone to explicitly allow logic gates
after users had found out how to create them out of flowing water and other
select blocks.

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gowld
Minecraft construction is weird. Minecraft's reason for existing is that
people think it's fun to make simple things mind-numbingly hard by using the
crudest lowest-level building blocks, each block simualting with horridly
monstrous gobs of computing powes).

So it's the worst of both worlds -- an expensive simulator for tediously
manipulting low-level primitives. Why not manipulate primivitives efficiently,
or use high-level constructs?

Then serious Minecraft constructors build mods and tools to automate the
tedium back out anyway, so they design whatever nice things using high level
tools, but then execute and inspect the builds on inefficient computing
systems of cryptocurrency-level of wastefulness.

Why not just make whatever thing you want out of good (virtual or physical)
materials in the first place, and then put it under the
microscope/oscilloscop/decompiler/hex-editor to marvel at its complex
structure?

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natpalmer1776
To actually answer your question: Barrier of Entry.

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Kiro
Pretty sure the people building calculators in Minecraft are on a CS level
where the Barrier of Entry is no problem.

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DonHopkins
I love how it combines dangerously antagonistic elements like water and
electricity. Somebody's going to get hurt!

In that vein, can you build logic gates out of cars and pedestrians?

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t0mek
Idea for the sci-fi story: after the civilization collapse, the only computing
device that has survived is an arcade machine, with a difficult game that
accidentally is Turing complete. People need to program it, so they can use
the results to reboot the power/transportation/medical equipment/etc.

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aduitsis
A similar thing is described in Cixin Liu's "The Three Body Problem", where
soldiers holding flags emulate the circuitry of a computer.

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tomclive
I really enjoyed that part of the book. If I remember correctly, the soldiers
were just representations of the Trisolarans as they were too alien for us to
identify with. The actual Trisolarans emitted light to build their living
computer.

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drainyard
Doesn't Turing completeness require conditional loops? Considering the fact
that he has AND and OR gates he can represent conditionals, but he doesn't
show it. And the fact that it always terminates by design also means it solves
the halting problem which by definition means it isn't Turing complete (I
think?).

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lou1306
What do you mean by "it always terminates by design?"

However, as the comments to the post say, the author should provide a proof
that the "game physics" allows to construct a functioning latch from these
logic gates.

Conditional loops are not essential: the lambda calculus is TC despite lacking
any loop primitives.

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entropy_
In theory you can build a latch using only NAND gates, so it should be
possible unless the gates that are demonstrated are flawed somehow, see my
sibling comment.

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Causality1
I could very well be dead wrong about this, but isn't any game that allows you
to construct the equivalent of a transistor turing-complete with enough work?

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seaish
Kind of, but the interesting part is finding out how to make the transistor in
the first place. These things usually take a few years to be found despite the
popularity of such games.

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espressomachiat
What does turing complete mean?

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dhagz
In the most basic sense, you can make a computer with it.

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ngcc_hk
Always wonder what happen if you are alone in a primitive society.

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em-bee
so douglas adams was right, the earth is just a giant computer

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jepler
Intended link may be [https://medium.com/@balidani/cities-skylines-is-turing-
compl...](https://medium.com/@balidani/cities-skylines-is-turing-
complete-e5ccf75d1c3a) \-- an edit link was posted by mistake

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0xdada
Argh! That's my bad, I can't seem to edit it now.

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dang
We've replaced the link above.

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jakear
Wait a tick. I can’t open medium at all, says I _must_ log in. Is this a new
thing?

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0xdada
My mistake, it was an edit link I posted, it should be accessible without
Medium, I also opted out of the monetized content thing.

