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!
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Non-deterministic Finite Automata | Sipser Example 1.16
I am working through the Sipser Book (2nd edition) and came across this example, which I do not understand. In the book it states that this NFA accepts the empty string, $\epsilon$.
Could someone run ...
1
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0answers
51 views
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 ...
3
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2answers
45 views
In what sense are dataflow architectures non-deterministic?
The Wikipedia article mentions non-determinism in the context of dataflow architectures. Arthur Veen's paper mentions non-determinism when it elaborates on MERGE nodes as conditional constructs.
Are ...
2
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1answer
23 views
Why “Choice Points” introduce non-determinism in a program?
I'm studying the didactic programming language Oz, following the book "Concepts, Techniques, and Models of Computer Programming".
In the book, the nondeterminism is introduced through the concept of ...
0
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1answer
55 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 ...
1
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2answers
32 views
Describe in words how a NTM can simulate a DTM
I have this assignment
Describe in words how a DTM can simulate a NTM
Describe in wordshow a NTM can simulate a DTM
I'm working on this request and I'm crushing with the comparison.
1-I ...
1
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0answers
32 views
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) ...
0
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0answers
19 views
Proving the Complement of a DCFL is DCFL [duplicate]
If I Have a DCFL $L$ ( a CFL which can be recognised by a DPDA ),
How do I prove that $\overline{L}$ is also a DCFL
I checked my textbook for a proof but I wasn't able to understand the language.
Can ...
3
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1answer
49 views
If $NP\subseteq DTIME[n^{O(\log n)}]$ then what happens?
If $NP\subseteq DTIME[n^{O(\log n)}]$ then what happens? Does it imply $NP\neq EXP$? Is there any other consequences such as $BPP\neq EXP$? Does it also give $PSPACE\subseteq DTIME[n^{O(\log n)}]$?
2
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2answers
73 views
Why cannot we enumerate all Turing machines that have no fixed point?
The language
$$
L_1 = \{w \in \{0, 1\}^\ast \mid \exists x \in \{0, 1\}^\ast\colon M_w(x) = x\}
$$
($w$ is an encoding of a DTM, $M_w$ is the respective DTM.)
is not decidable, according to Rice's ...
7
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0answers
77 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 ...
1
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1answer
63 views
How do I construct a NTM that accepts the language consisting of the coding of turing machines that halt on one input?
I currently have a problem with the following question:
Let $L = \{ \langle M \rangle \mid \exists w: \text{$M$ halts for $w$ in at most $|w|^3$ steps} \}$.
Construct an NTM (non-deterministic Turing ...
5
votes
1answer
98 views
The definition of weakest precondition for a non-deterministic language
In the classical IMP language, the definition of weakest precondition is:
definition "wp c Q s ≡ ∃t. (c,s) ⇒ t ∧ Q t"
This is stating that from state s, after ...
1
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1answer
61 views
The Law of Excluded Miracle in the language of guarded commands
The definition of weakest precondition is familiar (let me use Isabelle's syntax here):
definition "wp c Q s ≡ ∃t. (c,s) ⇒ t ∧ Q t"
the weakest precondition ...
1
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2answers
210 views
What to do with empty set during NFA to DFA conversion?
I am currently converting this NFA to a DFA
I have come up with the following DFA:
...
1
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2answers
42 views
Understanding Hamiltonian Path, NP vs Co-NP
I am having difficulty understanding the distinction between NP and Co-NP.
According to my textbook (Sipser), the HAMPATH problem is in NP. That is, for the language: HAMPATH = { (G,s,t) | G is a ...
1
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1answer
377 views
PDA of the language where the number of a's are NOT equal to the number of b's
I have this NPDA for language L = {w: num_a(w) == num_b(w)}
all loops in q1
...
0
votes
1answer
55 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, ...
3
votes
0answers
29 views
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....
2
votes
2answers
290 views
Why SAT Requires A Non-determinstic Algorithm?
I am getting started to understand the probelm of Satisfiability and i am reading (Computers and Intractability: A Guide to the Theory of NP-Completeness).
I do understand the difference between a ...
1
vote
1answer
170 views
How to implement a maximal munch lexical analyzer by simulating NFA or running DFA?
I'm planning to implement a lexical analyzer by either simulating NFA or running DFA using the input text. The trouble is, the input may arrive in small chunks and the memory may not be enough to hold ...
1
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2answers
348 views
Understanding $\epsilon$ transitions on NFA
I can't understand why $\epsilon$ is accepted. I thought if $\epsilon$ is inputed then it would go from $q_1$ to $q_3$. $a$ is also accepted, but I though if $a$ is inputed then then the NFA would die,...
4
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1answer
123 views
How do non-deterministic algorithms work on current machines?
I have some questions regarding the exact nature of non-deterministic algorithms. Is it right that non-deterministic algorithms do not rely on any randomness whatsoever? In which case, this Wikipedia ...
2
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1answer
42 views
In certificate view of NL can we force the guesses to be in some format like $a^n b^n c^n d^n$?
In certificate view of NL the size of our guess can be polynomial.Can this guesses be like $a^n b^n c^n d^n$. Can we force the guesses to be in some format? I think it(the format) can be in regex ...
0
votes
1answer
93 views
Drawing a NFA for a string
I have these grammar rules defined as follows,
FDL -> FDEF FDL | ε
FDEF -> #feature #: FEXP
FEXP -> #op #( FLIST #)
FLIST -> FEXP #, FEXP | #feature
...
1
vote
1answer
42 views
Can we call deterministic equivalent of all NFA to be finite
Finite automata is defined as a simple machine having small memory. A deterministic equivalent of a NFA with n states will have O(2^n) states,so the number of states grow exponentially. So can we ...
1
vote
1answer
41 views
What will happen if input is larger than required in a NFA
This is my first time in the field of TOC so I am not able to provide any self-approach while asking .In the above example what will happen if input string is "1001" or "1111"?The state q4 can be ...
1
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2answers
86 views
NP Class Definition of a Certificate
Given the definition for all x ∈ Σ∗
x ∈ L ⇔ ∃ u ∈ Σ∗ with |u| ≤ p(|x|) and M(x, u) = 1
Lets say the input x = ababab
Then the certificate u shouldn't be longer than p(|x|).
But what would be p(|...
3
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0answers
40 views
How to prove existence of the language
Consider such question:
(Prove or disprove) There exists a language in $TIME(2^{n^2})$ that is not in $NTIME(n)$.
I guess that answer is yes because $TIME(2^{n^2})$ and $NTIME(n)$ are totally ...
0
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1answer
130 views
Are there any estimated, imperfect or fuzzy sorting algorithms?
I'm implementing some estimation metrics that take samples of optimisation functions and estimate their properties. One of the metrics requires the data to be sorted; however, since the metric is only ...
2
votes
1answer
113 views
Can an algorithm be truly non-deterministic?
I read the term "non-deterministic algorithm" in many places but I don't see how an algorithm can be truly non-deterministic. Typically, there is some source of randomness in these algorithms. If the ...
2
votes
1answer
3k views
Understanding trap and dead state in automata
Well, this sounds somewhat basic definitions, but I feel they needs to be clearly defined.
In book by Hopcroft et. al., there is an excerpt:
...a dead state, that is, a nonaccepting state that ...
1
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2answers
527 views
Number of states in NFA and DFA accepting strings from length 0 to n with alphabet Σ= {0,1}
The question is in title. Let me repeat:
What are the number of states in NFA and DFA accepting strings from length 0 to n with alphabet $\Sigma = {0,1}$
I feel both NFA and DFA will take ...
0
votes
1answer
58 views
Is this language NP Hard?
$L=\{$$($$m$,$w$,$n$$)$| $m$ is an encoding of a non-deterministic Turing machine, $w$ is any word/string in the closure of alphabet, i.e. $w\in\Sigma^*$, $n$ is any positive integer, i.e. $n\in\Bbb{Z}...
0
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0answers
59 views
Where is proof that palindrom language is nondeterministic? [duplicate]
It is well-known that the language over $T$ with at least 2 symbols is nondeterministic. for simplicity, the language $\{ww^R: w\in\{a,b\}\}$ (even-length palindroms of $a$, $b$) is context-free, but ...
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2answers
52 views
Do NFAs with $\varepsilon$-moves never terminate?
Suppose in an NFA we have an $\varepsilon$-move from a state $q_0$ to $q_1$. According to Sipser,
Without reading any input, the machine splits into multiple copies one following each of the ...
1
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1answer
51 views
Questions on Sipser's NP implying verifiability?
I've revisited trying to understand the proof to why NTM exists iff there is a verifier. I think I'm finally understanding the proof but I want to make sure and thus have some questions as follow up ...
0
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1answer
32 views
NFA accepting $L=\{wbbav \;|\; w \in \{a,b\}^*, v \in \{a,b\}^+, v\; has\; suffix\; a\}$
I have to construct NFA that accepts language $L=\{wbbav \;|\; w \in \{a,b\}^*, v \in \{a,b\}^+, v\; has\; suffix\; a\}$.
My solution is this automata:
Can you tell me, if this is correct or not? If ...
0
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1answer
352 views
Is every decidable language a deterministic context free language?
I'm trying to get a better understanding for the relationship between decidability and a few other things so that I can get a better grasp of the topic. Any info helps!
Is every decidable language a ...
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3answers
110 views
Is there a method to compress all data without loss (lossless compression)?
I know that the answer is no but I'm not sure why. Here's where I started. We know that all data with length $n$ Bits and minimum $1$ Bit can be compressed, either lossless or lossy. But how do I ...
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0answers
90 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. (...
5
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1answer
149 views
Implications of $NL=P$
What would be some implications of $NL$$=P$? Would it be possible to get recommendations on good sources/papers I can read to learn more about this? Thank you
4
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1answer
94 views
Prove: if $\delta_D(q0, w) = p$ then $\delta_N(q0, w) = {p}$
In my textbook, it presents the theorem, "A language L is accepted by some DFA if and only if l is accepted by some NFA". My textbook explains that the "if" portion of the proof is given by the subset ...
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3answers
239 views
Minimal DFA with more states than its equivalent NFA
I understand that using a bad case for subset construction as provided through an example in the book - Introduction to Automata Theory, Languages and Computation, we can definitely have an NFA with $...
4
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1answer
116 views
Complement of Mealy machine
How could one reasonably define and construct the complement of a deterministic Mealy machine?
My intuition is that the complement should give exactly the opposite of output strings after a specific ...
0
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1answer
81 views
Constructing an FSA, where Ratio of number of states of FSA to its Minimal DFA Equivalent < 0.5
I need to choose a language, design a finite automaton M such that L = L(M). Construct a minimum-state DFA M′ equivalent to M in such a way that the ratio of the number of states in M to the number of ...
4
votes
1answer
187 views
Why nondeterminism?
Theory of computation often involves nondeterministic models of computation. Some examples include nondeterministic finite automata (NFAs), nondeterministic pushdown automata (PDAs), and ...
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4answers
166 views
How do NFA's make program design any better when converted DFA form can't remember original states?
Here is some content from the book by Peter-Linz I read
"Consider a game-playing program where the machine needs to make the decision for the next move [say for tic-tac-toe]. Since there are ...
2
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0answers
90 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 ...
0
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1answer
94 views
Confused b/w non-deterministic finite state automata vs finite state automata
I am reading this example of FSA from book Martin & Jurafsky "Speech and Language Processing".
As per definition of FSA you can only transition to one state after consuming one input. In this ...
