Questions tagged [nondeterminism]

Questions about automata, formal grammars or other computation-models that specifically relate to the use of nondeterminism. Not to be confused with randomness or ambiguity!

34 questions with no upvoted or accepted answers
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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 ...
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200 views

Why does Non Determinism not enhance FA like it does for PDA

Both Deterministic and Non deterministic Finite Automata can recognize the same universe of regular languages. On the other hand, Deterministic Push Down Automata can only recognize a subset of ...
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Detecting loops in NPDAs

I'm aware that the halting problem is solvable for PDAs, but I have recently discovered that I am wrong about how to actually do it. I used to think that you could detect an infinite loop by meeting ...
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Which programming languages have a syntax that can be described by deterministic context-free grammars?

This question asks which programming languages have a syntax that cannot be described by deterministic context-free grammars - the answer is "Many [...] including Algol 60, C, and C++". Until ...
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1answer
54 views

motivation and idea of defining non-deterministic Turing machine

This is a very basic question but I spent some time reading and find no answer. I am not computer science majored but have read some basic algorithm stuff, for example, some basic sorting algorithms ...
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What is the difference between the choice operator and nondeterminism in CSP?

I'm learning CSP now for my research. First time doing formal work in CS. I'm having a hard time understanding the difference between choice $\square$ operator and the nondeterminism $\sqcap$ operator....
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38 views

Is it possible, at least in theory, to “lockfree-ize” algorithms algorithmically?

The problem emerged from a practical case, but thinking on it resulted more and more theoretical directions. Typically, the lock-free algorithms do relative simple things in the practice, but their ...
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30 views

Minimal regular expression from minimal NFA for finite language in polynomial time?

Given a minimal NFA for a finite language, is there a polynomial-time algorithm to find a minimal regular expression for the same language? This question is based on a recent question regarding ...
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102 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 ...
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315 views

Logarithmic space difference between deterministic and non-deterministic algorithms

I had an interview today, and the interviewer has told me about a theorem (of someone called Hill- or Hell-something) which states that for a non-deterministic algorithm there exists a deterministic ...
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39 views

What is $f(n)$ in $NTIME(n)\subseteq DTIME(f(n))$ if $CIRCUITSAT$ is in $P$?

If $CIRCUITSAT$ in $n$ variables and $m$ gates has an $O((nm)^c)$ algorithm for a fixed $c>0$ then $NTIME(n)\subseteq DTIME(O(f(n)))$ for large enough $f(n)$. What is the smallest $f(n)$ in $NTIME(...
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How to adapt proof of the ND time hierarchy theorem for alternate definition of NDTM?

For reference, the version of the nondeterministic time hierarchy theorem in question is this one: The relevant portion of the proof in question (also from Arora-Barak) is here: Arora-Barak define a ...
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Characterization of NFA whose equivalent (minimal) DFA has exponential number of states

(I don't know if there are standard names for this, so) Let's say that a Nondeterministic Finite Automaton (NFA) is $n$-expansive if it has $n$ states and any Deterministic Finite Automaton (DFA) ...
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350 views

Converting a non-deterministic context free grammar to deterministic

I have the non-deterministic context free grammar $$I \to abcX | abdY$$ $$X \to X d | \epsilon$$ $$Y \to XX |I$$ and i want to convert it into a deterministic. I know that the rules $I \to abcX | abdY$...
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222 views

Non-deterministic Turing Machine recognizing a context-free Language

This question is taken from an exam of a Computer Theory Course. Describe how a NON-Deterministic Turing Machine with two tapes recognize the language generated from the grammar: $ S \rightarrow SS ...
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Why can't a server provide guaranteed service with only bounded nondeterminsm?

The wikipedia page Actor Model and Process Calculi History, presents the following claim: The semantics [of CSP] provided bounded nondeterminism unlike the Actor model with unbounded nondeterminism....
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94 views

Dangling else determinism

The natural grammar for dangling "else" is ambiguous. But there exists an unambiguous version of the grammar that links the "else" to last uncompleted "if" statement. Is this version also ...
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330 views

NFA that accepts binary strings starting with 1 and with at least 01, or at least 010, or both

Im not sure if I am understanding this question correctly. Its a problem without a solution in my text. Starting with 1, and at least 01 or at least 010 or both these substrings..... So a regular ...
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547 views

K -> 2 tape reduction for nondeterministic Turing machines

How to I show that any language in NTIME(T(n)) can be accepted by a non-deterministic 2-tape O(T(n)) time-bounded Turing machine, with modifiable input tape? I've seen the k to 2 tape reduction for ...
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51 views

apply the method of conditional expectations

For a Randomized vertex cover problem Why there is not much hope of deriving an efficient, deterministic version using the method of conditional expectation? I can assume the problem is not ...
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Problem in NP: $EQ1 = \{(p_1,…,p_n): \exists x_1,…,x_m\in Z \ p_1(x_1,…,x_m)=…=p_n(x_1,…,x_m)=0. \}$

I have to following problem to show is in NP class. $EQ1 = \{(p_1,...,p_n): \exists x_1,...,x_m\in Z \ p_1(x_1,...,x_m)=...=p_n(x_1,...,x_m)=0. \}$ Here $p_1,...,p_n$ are polynomials in m ...
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Push Down Automatas: Is it still an accept state if stack is not empty?

I'm currently seeing if a PDA is in an accept state give an input string. After reading the entire input tape, I am currently in the accept state. However, in the stack, there are two items in it. So ...
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1answer
85 views

NFA for all strings not containing 1010

if I want to design a NFA (that's NOT A DFA) that accepts the set of all strings that do not contain the substring 1010, is this correct? because I can just accept 1010 by capturing it in the starting ...
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Why is it not possible to prove the equivalence of nondeterministic and deterministic Turing Machines the same way as for NFAs and DFAs?

I found en excercise asking this question. I know that for proving the equivalence of NFAs and DFAs we can use the conversion through subsets, and that for proving the equivalence of nondeterministic ...
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109 views

show doubly connected graph is NL complete

The question:A directed graph is doubly connected if every two vertices are connected by a directed path in each direction. Let DCG = {| G is a doubly connected graph} Prove that DCG is NL-complete. (...
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How are Probability and Non Determinism Related ? Alternatives to handle Non determinism?

I have been thinking about Non-determinism in any kind of state machine. Since I work on machine learning, I tend to think that probability is a means of handling non-determinism. Instead of ...
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Generating a Covering Array Matrix with Simulated Annealing

I've been reading the following paper to understand how I can develop a non deterministic algorithm for test cases generation https://www.researchgate.net/publication/293043297_A_two-...
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129 views

Does for every NFA $N$ exist NFA $M$ that has maximum 3 final states and $L(N) = L(M)$

I have a question: Does for every NFA $N$ exist NFA $M$ that has maximum 3 final states and $L(N) = L(M)$. I can answer no for DFA for below language and its minimal DFA that has 4 final states . $...
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graph has at most 2017 connected components is in NL

I need to show that deciding whether a graph G has at most 2017 strongly connected components in in NL. After searching, i found a previous answer: Checking whether a digraph on $n$ vertices ...
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Reduce Nondeterminism in Pushdown Automata

I know there might be some situations where we want transitions to be only taken when the stack is empty, and transitions to be taken only when the input stream is empty. We can create an additional ...
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752 views

extended transition function for NFAs

Below I am using a DFA transition function that is extended to accept words instead of just symbols. Let's say it is given that the following information is true: $$\delta(q_0, 0^3) = \delta(q_0, 0^6)...
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1answer
181 views

What's the purpose of the non-deterministic Turing machine?

(*) Acronyms NTDM := non-deterministic Turing machine. TM := deterministic Turing machine. (*) Consider the following idea The NTDM is able to follow, in parallel, all paths of the tree of the ...
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59 views

Given a NP Algorithm for SAT, do we expect to have Correct and Incorrect Solutions?

I am reading about Boolean Satisfiability Problem and Nondeterministic Algorithms, in the latter defination it says : In computational complexity theory, nondeterministic algorithms are ones that, ...
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What input does this NFA accept?

I'm trying to find out what strings this NFA would accept. From what I understand, an empty string would work, as well as any string that has nothing but 0's. But for strings containing 1's, I'm a ...