July 25th, 2024

The Infinity Machine

The Infinity Machine, by Simon Tatham, explores a hypothetical computing environment with infinite speed, featuring an infinitely long memory line and minimal instruction set, raising questions about computation and memory limits.

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The Infinity Machine

The Infinity Machine, conceived by Simon Tatham, is a speculative exploration of a hypothetical computing environment where computers operate at infinite speed. This work does not follow a traditional narrative structure but instead delves into the technical implications of such a machine, appealing primarily to computer programmers and mathematicians. The concept originated from a remark in Ian Stewart's book, which suggested a light switch that could be toggled infinitely within a finite time, prompting thoughts on a computer capable of executing infinite computations in a similar manner.

The proposed architecture features an infinitely long memory line of bits, allowing for the separation of data into infinite substreams. This structure enables efficient memory management and supports various data types, including arrays of infinite size. The Infinity Machine operates on a clock system that can execute either a single instruction or an infinite sequence of instructions within one clock cycle, depending on the use of an "infinity" instruction.

The instruction set is minimal yet powerful, incorporating basic operations and the ability to perform complex computations through infinite sequences. Tatham's exploration raises intriguing questions about the nature of computation and memory in a world where infinite processing is possible, while also highlighting the challenges and paradoxes that arise from such a concept. Overall, The Infinity Machine serves as a thought experiment that invites readers to consider the boundaries of computing and mathematics.

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By @cvoss - 3 months
If such a machine existed in our universe, as it sped up its execution, its parts would approach the speed of light. To continue speeding up its execution, it necessarily must occupy a smaller and smaller volume, to keep the parts nearer and nearer to each other. Continue further, and you realize that the total information content of the machine can't be sustained at any amount without the thing collapsing itself into a black hole. So, even if the machine, in any sense, "finishes" the computation, the output will live inside a black hole and thus be physically unknowable to us.

I find it so fascinating that fundamental properties about the laws of physics integrate so tightly with what is computable. The standard definition of compatibility involving Turing machines sounds kind of arbitrary, but those machines are representative a truly fundamental concept in our universe: that which is physically knowable, since you can build Turing machines out of the stuff in the universe.

Almost. Turing machines have unbounded tape. But the universe does not contain an unbounded amount of information or space with which to work. Sufficiently large Turing computations, though theoretically finite, are not realizable in our universe. Should such computations be considered decidable or undecidable?

By @Schiphol - 3 months
There's work on so-called "hypercomputation" that might relevant to the author's project: https://en.wikipedia.org/wiki/Hypercomputation
By @tlocke - 3 months
I know the light switch idea as Thomson's lamp:

https://en.m.wikipedia.org/wiki/Thomson%27s_lamp

I used it as an interview question many years ago. I wasn't very rigorous about it, basically any plausible answer was good enough for me. Answers fell into two categories, the theorists (it's an infinite series that doesn't converge) and the pragmatists (you couldn't physically do it).

By @rahimnathwani - 3 months
Tangential:

1. Simon Tatham is the author of PuTTY

2. In the early days of the web, many people's personal sites were hosted on shared computers (e.g. my first was on my university's DEC Ultrix system). The URLs started with a reference to the user's home directory. This page is hosted on a machine that has a page to lists all the user's home pages: https://www.chiark.greenend.org.uk/users.html

3. The home page has this awesome spam detector:

  If you want not to be able to send mail here in future, please send mail to tabasco@chiark.greenend.org.uk.
By @VikingCoder - 3 months
I'm once again reminded of the book Permutation City...
By @sqeaky - 3 months
Such a machine would be fun

I would make a programming language where you couldn't write code, only detailed specifications and tests. In a VM Every possible permutation of bytes/opcodes/instructions/whatevers would be tests to produce the smallest and fastest (presuming the code is to run on other machines) possible binaries that pass your tests. Ideally this would produce a Pareto front of possible outputs and you could choose from among them.

Another idea solving old problems the hard way. Since fermat's last theorom is countably infinitely problem and this computer is uncountably infinite in performance it should be able to knock it instantly by simply enumerating all integers and trying them.

By @sqeaky - 3 months
If we used such a machine to to enumerate Pi what would happen? Is it proven that Pi infinitely long? If so that would be a countable infinite because it is digits of precision, right?

Could we write algorithms that search all the digits of pi for patterns? Or mayb messages on speculation of creators or others who might be able to tamper with it?

Could other math things be searched? Have we proven there is no upper limit to prime numbers? I know the largest known mersenne prime fills a novel sized book with just one number, but when does a number get too big to be prime if ever?

By @omoikane - 3 months
I thought it's interesting that the author went the way of add-more-via-subdivision. It feels very analog, kind of like how with old photos, the way you get more resolution is to just print them bigger (of course, what you actually get in reality is more grain).

It's different from how we modeled things like Turing machines, where if we needed more memory, we would append more tape, as opposed to subdivide the existing tape further.

By @gwern - 3 months
By @Demonoculus - 3 months
While I am not an expert, but won't it run into Xeno's like paradox? But makes for interesting reading.
By @mistermann - 3 months
With the plunging cost/capability of AI compute, variations of this are becoming more plausible every day. Who will be the first mover?