# 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.

64 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
1answer
298 views

### Machines for context-free languages which gain no extra power from nondeterminism

When considering machine models of computation, the Chomsky hierarchy is normally characterised by (in order), finite automata, push-down automata, linear bound automata and Turing Machines. For the ...
1answer
547 views

### Turing Machine-Like Formalism for The Actor Model

Turing machines have a formal symbol alphabet, state and transition-rules based description of how a computation is done. The Actor Model is sometimes mentioned as a more powerful computational-...
0answers
80 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 ...
0answers
127 views

### Make a tag system simulate a finite automaton?

Tag systems are Turing-complete. I was wondering if there is any easy way to create tag systems that simulate finite automata. So create tag systems that recognize languages, e.g. by having at the end ...
2answers
298 views

### Automaton equivalent of the π calculus?

If Turing Machines are the automata equivalent of the $\lambda$ calculus, what is the automaton equivalent of the $\pi$ calculus? I suppose it would be some class of automata that resembled a Turing ...
1answer
776 views

### What is the difference between quantum computing and parallel computing?

Quantum computing essentially relies on the fact that qubits maintain multiple possible states simultaneously. Parallel computing too processes multiple states simultaneously. So what is the ...
0answers
196 views

### Computational power of Actor Model

In the question below, let TM be Turing machine, NTM be nondeterministic Turing machine and PTM be probabilistic Turing machine. In his paper "Actor Model of Computation: Scalable Robust Information ...
0answers
91 views

### Model Join calculus as hypergraphs

I'm not sure if this is the right site to ask, but I couldn't find a another one. Some time ago I found out about the join calculus. It is based on constructs called joins to support concurrency. For ...
0answers
37 views

### The cost of memory allocation on the (tacitly assumed) Word RAM machine?

Consider a particular algorithm that solves the binary search problem (or similar stuff) by performing $\sqrt{n}$ simple operations on numbers of $\log(n)$ bits. Suppose this algorithm works on a <...
0answers
55 views

### Real RAMs with “reasonable” operations

There is a large body of literature on RAMs with "reasonable" and "unreasonable" operations, where "unreasonable" operations would yield a machine with too much power to be practically feasible. For ...
0answers
105 views

### Is a reduced Wang B-machine Turing-complete?

A Wang B-machine has only 4 instructions: right: Move tape head right left: Move tape head left ...
0answers
62 views

### What is the role of abstract machines in the Curry-Howard isomorphism?

By abstract machines I mean things like the SECD machine, Krivine's machine or more generally machines with states/memory/registers/stack/accumulator... According to Wikipedia page of the Curry-...
0answers
34 views

### Computational complexity of emulating (untyped) λ-calculus with a queue machine

I am looking for bounds - both lower and upper - on the time, spacial, and state/symbol (i.e. number of states and symbols required) complexity of simulating the (untyped) λ-calculus with a queue ...
1answer
663 views

0answers
83 views

### Why does using an encoding trick like Gödel numbers make a register machine universal?

Here the author describes the Random Access Stored Program machine and the problem of indirect addressing. The author states: But this does not solve the problem (unless one resorts to Gödel ...
0answers
109 views

### 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 ...
0answers
37 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 ...
0answers
200 views

### What is the relationship between “model of computation” and “algorithm”?

Traditionally, the usual definition you find for model of computation is "an abstract description of how an output is computed given an input" (Wikipedia and my TCS course are my sources, but the ...
0answers
98 views

### Simulating QC using nondeterministic Turing machine

Is it more efficient to simulate Quantum Computer using a non-deterministic Turing machine? Would it be more efficient than simulation using a deterministic Turing machine or probabilistic Turing ...
0answers
76 views

### Is the set of admissible numberings recursively enumerable?

For each admissible numbering, pick at least one pair of programs (but not necessarily all, which is impossible anyway) where the first translates from a given admissible numbering to that one, and ...
0answers
324 views

### Explaining TM notation in Lewis/Papadimitriou

I was working on some questions in the book "Elements Of The Theory Of Computation", by Lewis and Papadimitriou, and I need help with one question - question 4.1.8 (chapter 4): Give the full ...
0answers
49 views

### Typed representation of a memory model

Assume a simple procedural language, where statements write and read from local memory via references and procedures accept arguments of n different scalar types (say floats, ints and strings) and ...
0answers
97 views

### ORAM: Is it generic?

Recently, plenty of researchers are looking at designing efficient data-oblivious algorithms. Roughly speaking, an algorithm is said to be data-oblivious if its data access patterns are independent of ...
0answers
45 views

### A linear code, what is that?

I have been trying to understand the polytope model used for loop nest optimizations. Now while going through some of the thesis written on this, i came across the term/phrase "linear code" a number ...
0answers
64 views

### Expressing classic automata in modern terms

This semester I was introduced to finite automata (FSM), then pushdown automata (PDA), and now the Turing machine (TM). Granted that there're many possible implementations of these abstractions (...
0answers
68 views

### NPDA, guessing capability and stack as an exclusive resource

Context Free languages is exactly the class of languages recognized by Nondeterministic Push Down Automata (NPDA). We can view a nondeterministic transition as a guess; for example if $L = \{x x^R \}$...
0answers
562 views

### λ-Calculus extensions: meaning of extension symbols

When working with λ-Calculus I see lots of extensions that use other symbols such as ∀ <:Top {} ←, which are from "Types and Programming Languages" (WorldCat) by Benjamin C. Pierce. ...
1answer
13 views

### Injectivity verification in o(n) space and O(n) time

The problem I want to solve is this: Given a list $A$ of $n$ elements, I want to verify that they are all distinct. If I were to do this "myself", I would need $O(n)$ space and $O(n\log n)$ time to ...
0answers
26 views

### Theory for programs that are “embedded” in other programs?

We can make the following distinctions: (I will use the term "program" and "machine" as synonyms). A (baseline) machine. This can be formalized by a Turing machine. It receives an input, and computes ...
0answers
24 views

### General notion of memory for a computational model

I have just started studying Michael Sipser's Theory of Computation, studying various computational models such as FAs, PDAs et cetera. In the book, the term "memory" was often used,as in the case of ...
0answers
51 views

### 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 ...
0answers
31 views

### Alternatives to Sequential Computation

When software boils down to assembly, it is just a sequence of instructions like this: ...
0answers
95 views

### Doubt on dovetailing

Let < M > be an encoding of a Turing machine. L = { < M > | M is a Turing machine that accepts a string of length 2014 } Above language is R.E(even though we have infinite TM's) as we have ...
0answers
56 views

### Formal definition of simulation

Assume that the model of computation is a standard Turing machine model with input alphabet $\Sigma = \{0,1\}$, work alphabet $\Gamma = \{0,1,\_\}$, 1 input tape, 1 work tape and 1 output tape. We ...
0answers
87 views

0answers
33 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 ...