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Computation as a universal and fundamental concept

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31–40 of 183 posts

Re: Computation as a universal and fundamental concept

#31
post #2

Computation has turned out to be a far more general concept than I think was imagined, up to the point that many computer scientists now seem to equate computation with the functioning of the universe. Recently it's been shown that there are real, physical processes which are undecidable (we cannot know if a latice of atoms has a spectral gap or not, we cannot determine if a specific particle in a fluid flow will rea…

Undecidability is a problem of answer-extraction from a process, it doesn’t preclude the process from executing deterministically. The universe could well be the live execution of a deterministic, even basic algorithm, with all kinds of questions about its execution being undecidable.

Re: Computation as a universal and fundamental concept

#32
Is 'computation' really universal and fundamental? Turing machines, lambda calculus, algorithmic notations, they're all human-made formalisms. Are the halting problem and the limits of computability actually constraints that exist only within these human-made formal systems?

When we constrain a formalism to reduce complexity, it feels like necessity emerges from within those constraints. For example, when we say 'CRUD app,' we immediately think of a specific pattern. In the same way, once you adopt a 'form,' the constraints that come with that form progressively expand the state space. In that sense, it feels like both discovery and invention.

Famous mathematicians and scientists often distinguish between model and reality, yet we tend to mistake the model's shape for reality itself. People like John Wheeler and Stephen Wolfram argue that computation is a fundamental property of the universe. But can we really say that when we downcast reality to fit human cognition, losing information in the process, and then upcast it back, the information is fully restored? I always find this point difficult.

Landauer's principle says that abstract logical operations, information erasure, necessarily increase physical entropy. That shows there's a thermodynamic cost to physically implemented information processing. But I don't think that proves computation is fundamental.

Whether it's computation or geometry, they're all abstract formalisms created by humans. But when we actually measure things, they're subject to physical laws. Still, whether that makes them fundamental is a difficult question. I think these are just results of the process where humans name phenomena and constrain them. I don't think they're the cause.

You can define computation broadly enough, as 'a process where a state changes to another state according to rules,' to make almost everything look like computation. But being able to explain something with computation and claiming that computation is fundamental are different things, aren't they?

Meaning exists within the structures and constraints of human-made formalisms. We artificially lower cognitive complexity and translate things into human language. Whether that's fundamental, I'm not sure.

Maybe I'm a reductionist. Plenty of intellectually brilliant scholars make those claims, but people like me, with slower minds, end up thinking these kinds of stupid thoughts. I wish I could organize my own thoughts bette

Re: Computation as a universal and fundamental concept

#33
Discrete math and Algorithms were two of my favorite college classes. They were really the only part of computer science that was mind blowing. The rest was software engineering, which was transparently "possible". Like, yes, big programs and OSs and numerical models exist, and yes I will graduate and work with them and add to them, someday, yeah sure.

But decidabilty, Godel's theorm, busy beaver numbers, etc... those were unexpected and worth the price of admission.

Thanks Prof Hadas, you made it fun to have my mind blown.

Re: Computation as a universal and fundamental concept

#34
post #9

Something has always nagged me about the halting problem, might be my mis-understanding of the problem space but; - You have a piece of software - That software does in memory compute only - The software does not touch any peripherals, networking, or any other external source which introduce unpredictability (x) I'm convinced that somehow this can be solved/proven whether the execution will halt or not. (x) The secon…

For the finite case, the more relevant question is, can you predict whether or not the computation will halt in less time than 1. executing the algorithm and 2. checking whether or not the algorithm ever loops?

Bear in mind checking whether or not the algorithm ever loops means taking the full state of the system and checking against a database of all previous states of the system. Bear in mind that the Atari 2600, and its whopping 128 bytes of RAM, has with that amount of RAM more states than there are planck volumes * planck time intervals in the known universe... by over sixty orders of magnitude. And every three additional bits you add to the RAM of the system your are looking at adds an order of magnitude (minus a bit) to that, so, nearly 3 orders of magnitude more states per byte... not per megabyte or gigabyte, per byte. Call it 2 orders of magnitude per byte if you want to be conservative.

It can be solved, if by nothing else simply by running it, in the mathematical sense. In the practical sense it's not even close. That's why we use the Turing machine analysis... technically it's an approximation because we don't actually have real Turing machines. However the size of the finite state machines we have is such that it is far more productive to simply say "the halting problem is unsolvable" than to argue about how many orders of magnitude of orders of magnitude of resources it takes to solve the question of whether or a given program terminates.

Re: Computation as a universal and fundamental concept

#35
post #9

Something has always nagged me about the halting problem, might be my mis-understanding of the problem space but; - You have a piece of software - That software does in memory compute only - The software does not touch any peripherals, networking, or any other external source which introduce unpredictability (x) I'm convinced that somehow this can be solved/proven whether the execution will halt or not. (x) The secon…

You might enjoy the book Escher Gödel Bach, the Eternal Golden Braid by Douglas Hofstadter, which will open up the world, power, and "danger" of proofs using contradiction to you.

Bonne lecture !

Re: Computation as a universal and fundamental concept

#36
post #2

Computation has turned out to be a far more general concept than I think was imagined, up to the point that many computer scientists now seem to equate computation with the functioning of the universe. Recently it's been shown that there are real, physical processes which are undecidable (we cannot know if a latice of atoms has a spectral gap or not, we cannot determine if a specific particle in a fluid flow will rea…

One sentence I heard somewhere wraps up the totality of computing:

"If Mathematics is the 'what', Computer Science is the 'how'".

This applies to each and everything.

Re: Computation as a universal and fundamental concept

#38
post #2

Computation has turned out to be a far more general concept than I think was imagined, up to the point that many computer scientists now seem to equate computation with the functioning of the universe. Recently it's been shown that there are real, physical processes which are undecidable (we cannot know if a latice of atoms has a spectral gap or not, we cannot determine if a specific particle in a fluid flow will rea…

One sentence I heard somewhere wraps up the totality of computing: "If Mathematics is the 'what', Computer Science is the 'how'" . This applies to each and everything.

If two people agreed on that statement, its entirely unclear if they agree with each other and if they found something profound in the first place.

The imo much more foundational relationship not everybody is aware of is https://en.wikipedia.org/wiki/Curry%E2%80%93Howard_correspon...

Re: Computation as a universal and fundamental concept

#39
post #9

Something has always nagged me about the halting problem, might be my mis-understanding of the problem space but; - You have a piece of software - That software does in memory compute only - The software does not touch any peripherals, networking, or any other external source which introduce unpredictability (x) I'm convinced that somehow this can be solved/proven whether the execution will halt or not. (x) The secon…

You might enjoy the book Escher Gödel Bach, the Eternal Golden Braid by Douglas Hofstadter, which will open up the world, power, and "danger" of proofs using contradiction to you. Bonne lecture !

Thank you for the suggestions, I look forward to reading!

Re: Computation as a universal and fundamental concept

#40
post #2

Computation has turned out to be a far more general concept than I think was imagined, up to the point that many computer scientists now seem to equate computation with the functioning of the universe. Recently it's been shown that there are real, physical processes which are undecidable (we cannot know if a latice of atoms has a spectral gap or not, we cannot determine if a specific particle in a fluid flow will rea…

> Recently it's been shown that there are real, physical processes which are undecidable

According to the currently known laws of physics. Which we know are incomplete/incorrect in several places.

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