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# Questions tagged [computation-models]

The definition of the set of allowable operations used for computation and their respective costs. Some examples of models include Turing machines, recursive functions, lambda calculus, and production systems.

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28 views

### Would models of computation in other conceivable universes be Turing complete?

I'm interested in gathering some references that discuss the topic of the relationship between computation and physics. Specifically, I'm interested in investigating two points of view: our current ...
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### How does one program in a tag system?

I've played with 2-tag systems a bit and read all about tag/lag systems. They're great for experimenting with computation, and obviously useful as intermediaries in various proofs. My question is: ...
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### How to model most optimized encoding of string data

Sorry if this question isn't super well defined, I am just struggling currently with figuring out what an "ideal solution" looks like to the following problem, and haven't pinned down an equation. I ...
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### Why no DPDA can accept Palindrome? (according to this proof)

This proof is from the book "Introduction to Languages and the Theory of Computation" by John C. Martin. My question is from the pink part at the second page: It follows in particular that no ...
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### Can differennt computation model lead to different complexity?

There are many examples where someone replaces a CPU with a GPU or an FPGA and get a performance boost of $\times 100$ or more, but is it possible for a change in the architecture of computational ...
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### Formal definiton of RAM model with D disks of blocks B, fast memory M and P processors

In some articles I've read of RAM model with D disks of blocks B, fast memory M and P processors. Is there a formal deifition of that model?
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### What is difference between a formal system and a model of computation

I don't exactly know the difference--partly because I cannot find a mathematical definition for a model of computation (also why is this)?
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### What is the motivation behind “ Descriptive Complexity ”?

Time and Space are two commons parameters (and also natural parameters) to measure the complexity of the problem. I am not able to understand the motivation behind defining " Descriptive Complexity". ...
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### Examples of logic gates using non-standard models

These are the only ones I have been able to find online: Pulley Logic Gates Marble adding machine MARBLE COMPUTER LOGICAL AND GATE I would like to find some more discrete models like these (as ...
72 views

### Would any continuous model of the universe have/be based on hypercomputational laws?

I've read that when Turing-Church thesis is applied to the universe and physics, one of the three interpretations that we can use and is defended by some important physicists is that: "The universe ...
170 views

### Is arithmetic turing complete?

Maybe my question doesn't make sense, because I lack some more thorough understanding, but I was curious if arithmetic was Turing complete? As I understand it, a "model of computation" is a mechanism ...
83 views

### Automata that is Turing complete if you add a nondeterminism

Pushdown automata have an interesting property: non-deterministic ones belong to a different computational class than deterministic ones. This is in contrast to finite state and turing machines, for ...
42 views

### What is “Phrase structure grammar”?

I'm undertaking Theory of Computation Classes. I came across this sentence while studying Recursively Enumerable Grammar: Type-0 grammars generate recursively enumerable languages. The ...
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### Numbering of vertices in RAM model

I have read few research papers in which given a graph $G$ where $V$ denotes its vertex set and $E$ denotes its edge set. Model of computation is word RAM. "Without loss of generality assume that ...
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### What is the motivation behind restore model of computation?

The memory that stores the input is called the input memory. The memory that an algorithm additionally occupies during the computation is called the working memory. $\textit{Model of Computations}$ ...
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### Correctness proof: induction on sequence of steps, need a stronger claim?

Im trying to prove the correctness of the construction proposed in this site answer: a two stack PDA that simulates a Turing Machine. By "correctness" i mean to prove more or less formally that we can ...
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### Why a TM with infinite states can decide the halting problem?

Assuming we have a model of TM with an infinite number of states. The domain and range of the transition function are also infinite. Given a description of a TM $M$ and a string $w$ how can we use the ...
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### Can all Turing-computable problems be solved with a machine with finite tape and infinite controls?

We know all computer computable problems can be solved using the infinite tape and finite control system of the turing machine. Now think something different, let the tape is finite but the control ...
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### Equivalence between different Turing Machines and a definition of simulation

Im having some difficulty understanding how the following two concepts could be related. Equivalence between TMs as is commonly tought According to this site answer, to prove a standard TM model to ...
38 views

### Is the language $L$ of coded CFG's Turing decidable?

Consider the following language $L$ = {$<G><w>$ | $G$ is a CFG and $w\in L(G)$} Now, I wish to prove that $L$ is Turing decidable. My gut tells me to construct a Turing machine that ...
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### RO turing machine with finite memory

Consider the following: A weak TM is a TM with finite tape in size $k$ which can only read its input values. note: the tape size does not include the input length. I need to determine whether if the ...
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### Is there way to compare computing power used in two blockchains when every one of them is using different mathematical function as a Proof-of-Work?

If I am a Bitcoin node, I can evaluate two blockchains in terms of each one consisting of more Terahashes than the other and thus deduct which one is the "correct" one. There is impartial source of ...
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### Is there a common unit of measurement for comparison of computing power used to solve mathematical puzzles?

I just wanted to make sure if I'm reasoning correctly. So, if two computers are solving the same mathematical puzzle i.e. SHA-256 function of Bitcoin (finding nonce that satisfies difficulty target), ...
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### why can not NPDA is equal to DPDA?

I have recently read that turing machine can be remodeled to perform as PDA now, i have a question that since DTM = NDTM ( non deterministic Turing machine) then every DTM can remodeled to be NDTM ...