Questions tagged [complexity]
The complexity tag has no usage guidance.
77
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Turing Machine that stops after certien steps question
Let A be a decision problem such that:
A = {(M,x) | M turing machine that accepts x in 2^|x| steps}
show that A not in P.
How could I prove that A is not in P, I tried doing so using NL but
I thought ...
1
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0
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73
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Cheapest Insertion is $2$-approximation for TSP
Consider the Cheapest Insertion Algorithm on a complete graph with $n$ vertices, where each edge $uv$ has a weight $w(uv)$, and the weights satisfy the triangle inequality $w(xz)\leq w(xy)+w(yz)$ for ...
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68
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Direct fpt reduction from Weighted 3SAT to Weighted 2SAT
In parameterized complexity, for each fixed $q$, the problem Weighted $q$-CNF SAT is W[1]-complete. In particular, this means that one can turn a 3CNF formula $\varphi$ into a 2CNF formula $\varphi'$ ...
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1
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130
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Validity problem of intuitionistic two-variable logic
The two-variable fragment $\mathrm{FO}^2$ consist of those sentences of first-order logic $\mathrm{FO}$ in which precisely two variables occur (e.g. $\exists x \exists y \exists z R(x,y,z)$ is not a ...
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Any problems for which we know the complexity, but no algorithms with the same time?
I suddenly found myself wondering if there are any problems for which the complexity (time or space or anything else) is proven, say to be O(n^2), but for which the best known algorithms are worse ...
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1
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Recursive generic oracles
In
Fenner, Stephen; Fortnow, Lance; Kurtz, Stuart A.; Li, Lide, An oracle builder’s toolkit, Inf. Comput. 182, No. 2, 95-136 (2003). ZBL1025.68041, the authors go through a variety of generic oracles.
...
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1
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144
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Is QMA known to contain Co-NP?
Is QMA known to contain Co-NP? If not, would Co-NP being contained in QMA have any implications for other complexity classes. (e.g. Causing the polynomial heirachy to collapse.)
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241
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What is the impact of encodings of sparse structures on the complexity of the model checking problem?
Some preliminaries first.
Consider a purely-relational structure (a.k.a. database) $\mathfrak{A} = (A, R_1^{\mathfrak{A}}, \ldots, R_{|\tau|}^{\mathfrak{A}})$ over some finite signature $\tau = \{ R_1,...
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1
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Relative error estimation of a special type of GapP function
Consider the functions included in the complexity class GapP.
We know that approximating a function from GapP, in the worst case, to inverse polynomial multiplicative error, is #P-hard. Even correctly ...
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113
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Deterministic one way communication complexity for message with arbitrary length
Let Alice have a binary string of length $n$ that it wants to send to Bob along a one-bit communication channel. However, Bob does not know the length of the message.
I have been looking into ...
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What is the computational complexity of the fastest algorithm to compute Jordan canonical form for a matrix
Given a matrix, What is the computational complexity of the fastest algorithm to compute Jordan canonical form for the matrix? suppose the value of elements of the matrix and eigenvalue are complex ...
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5
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1
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133
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Different definitions of grammar complexity
It's known that there are different "kinds" of grammar complexity of language $L$ --- nonterminal complexity (minimal possible $|N|$ for grammar $(N, \Sigma, P, S)$ generating $L$), covering ...
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147
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Generating a pseudo random Rubik's cube in $O(n^{2+\epsilon})$ time
Recently I've begun considering how one could generate and solve an $n \times n\times n$ Rubik's cube for $n$ well over 10,000. To solve such a cube is feasible; easily implementable parallelizable ...
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CNF encoding of set cover - NExpTime-completness
Notation: given a CNF formula A over variables X, we write $[A(X)]$ for the set of valuations $v: X \to \{0,1\}$ such that $A(X/v)$ is true, i.e. the set of valuations that makes formula A true.
I ...
9
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139
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Is 4-Coloring restricted to graphs with crossing number 1 NP-complete?
Planar graphs are 4-colorable.
Determining if a planar graph is 3-colorable is NP-Complete.
A graph with a crossing number 1 (graph such that it can be drawn with $\le 1$ crossing) is 5-colorable.
...
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1
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Is there significance to the ratio of the time it takes to locate a problem's solution over the time it takes to verify the solution?
I believe I have found a problem, the solution to which can be verified in 0 time (the solution can only be located in non-zero time, however). As a result, the ratio of the time required to locate a ...
6
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2
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362
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On the complexity of a "list" datastructure in the RAM model
I am interested in the complexity of a data-structure equipped with the following operations (similar to a list):
insertion of an element at a given position within the list
deletion of an element at ...
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340
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The theoretical complexity of Go - The state of the art
What are the latest advances in theoretical complexity of Go?
I know some early works about the complexity of Go:
"Go is polynomial-space hard" proved that Go is PSPACE-hard.
"Ladders are PSPACE-...
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144
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Complexity of multi-objective optimization problems
How can we define and prove the worst-case complexity of multi-objective optimization problems (MOOP)?
It is easy to see that, if one of the objectives is an NP-Hard optimization problem, then the ...
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119
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Fast algorithm to find pair of triangles with a common edge in a complete graph
Suppose we have a complete graph with 4 nodes. To each triangle in this graph we assign a value $energy$ that is the multiplication of its edge weights. The question is to first find pair of triangles ...
8
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4
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627
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Constraints on sliding windows
Let $L\subseteq \Sigma^*$ be a language of finite words and $n>0$ some integer.
I would like to know if anything is known on the time and space complexity with respect to $n$ to check for ...
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Evidence integer multiplication is in linear time?
After millenia of quest we have identified two $n$ bit integers can be multiplied in $O(n\log n)$ time. Please refer details in https://www.quantamagazine.org/mathematicians-discover-the-perfect-way-...
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What is a natural problem in theory of computation?
In Stephen Cook's paper on the P vs NP problem,[1] he states the following [2]:
Feasibility Thesis: A natural problem has a feasible algorithm iff it has a polynomial-time algorithm.
My question ...
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260
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Does small circuits for a NP-complete problem contradict ETH?
The remarks of the Theorem 4 in the paper "On the complexity of circuit satisfiability" claims that: if circuit satisfiability (CktSat) problem can be decided by deterministic circuits of $2^{o(n)}$ ...
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825
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Is convex optimisation in P?
Consider a convex optimisation problem in the form
$$\begin{align}
f_0(x_1, \ldots, x_n) &\to \min \\
f_i(x_1, \ldots, x_n) & \leq 0, \quad i = 1, \ldots, m
\end{align}$$
where $f_0, f_1, \...
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Sentences in what kinds of grammar in the Chomsky hierarchy can be parsed by an LSTM of a given size?
Given
an LSTM $N$ of a given size $A$,
a sentence $S$ with a given number of words $B$,
a Chomsky grammar hierarchy level $C$ in 0-3,
a Chomsky grammar $G$ of level $C$ of size $D$,
A given fixed, ...
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70
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Looking for Research in Cryptographic Computing
I recall reading in college about a nascent research area regarding cryptographic techniques for secure computing, relating to zero-knowledge proofs, but I am having trouble remembering the exact term....
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SAT Solvers and their applications
I've been reading and learning about SAT solvers this week. If they can solve problems with thousands of variable quickly haven't we practically solved ANY problem that can be reduced to it, including ...
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Is there a counterexample to this work?
Is there a counterexample to this claim https://arxiv.org/abs/1610.00353? They claim a $O(n^6)$ LP model with simulations to support. I think asking validity is not a reasonable problem. However ...
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Error in paper "Some NP-complete geometric problems"?
The paper in question:
M.R. Garey, R.L. Graham and D.S. Johnson. Some NP-complete geometric problems .
This paper proofs the NP-completeness of some well-known problems, such as the Steiner Tree ...
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Paths of length $p$ in a Graph, $p$ a prime
I came across the following decision problem, for which I wondered whether anybody of you came across a similar problem and can give me some insight on its nature/complexity.
Given as input a ...
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Implications of resolving $BPP$ vs $PSPACE$
The relationship between the complexity classes $BPP$, $P$, and $NEXP$ is currently undetermined. We know that $P \neq EXP$ by the time hierarchy theorem, but we don't know if $BPP = P$ (as many ...
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Are these problems in NP class?
${\bf New\ version}$ [Version 1.2]
Let $f: \mathbb{N} \to \{0,1\}$ be a computable function, ${\bf Fin}(\mathbb{Z})$ be the set of all finite subsets of $\mathbb{Z}$, and $W: {\bf Fin}(\mathbb{Z}) \...
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Does $\textbf{PCP}[poly(n), O(1)] = \textbf{coRP}$?
Something has been buzzing me recently. It is well-known that $\textbf{PCP}[poly(n), 0] = \textbf{coRP}$, but does $\textbf{PCP}[poly(n), O(1)] = \textbf{coRP}$ ?
I have found a proof for this ...
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Petri net termination
Termination is the following problem.
Input: a Petri Net with initial marking
Output: "yes" iff there exists an infinite firing sequence. The naive algorithm in the case of bounded nets for example ...
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2
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810
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Formally Verified Complexity Theory
Is there any ongoing project to formally verify the theorems and proofs of complexity theory using a proof assistant like Coq? Are there any boundaries to doing this?
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Complexity of the Schönhage–Strassen algorithm
In the Wikipedia article, the complexity is listed as $O(n \cdot \log (n) \cdot \log (\log (n)))$, where $n$ is the number of bits.
Would the real bound be given by setting $n=\frac{b}{w}$, where $b$...
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1
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349
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Parallel Pebble Game on a Line
In the pebble game on a line there are N+1 nodes labelled 0 through N. The game starts with a pebble on node 0. If there is a pebble on node i, you can add or remove a pebble from node i+1. The goal ...
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How to shrink a very large sparse matrix [closed]
Let $A$ be a matrix where $A \in \mathbb{F}^{n^s \times n^s}$ and $s>2$.
Assume $A$ is a sparse matrix where its rank $\leq n$ and that there is only constant number of non-zero elements in each ...
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Complexity of comparison unary>binary
What is the smallest widely-known complexity class to which
$$\left\{\langle i,j\rangle\middle|\begin{array}{@{}l@{\ }l@{}} & i\ \text{is a unary encoding of a positive integer}\ \hat\imath\\\...
user44501
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1
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Why does not the definition of NP problems care about the complexity of guessing? [closed]
I have a question regarding the definition of NP problems. According to that, a problem is in NP if one can guess a certificate of polynomial size in polynomial time. However, this definition does not ...
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What's the complexity of factoring over a set of generators (say in $GL_2$)?
In particular, if I have some char-0 field $k$ (let's take $\mathbb C$ for now) and I consider $G = GL_2(k)$ with arbitrary nontrivial distinct $A, B \in G$. Then for some $C \in GL_2(k)$ do we know ...
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Is there any work that relates the liveness of a Petri Net to the complexity of determining coverability?
I'm working on a problem where the formalism appears to be an abstraction of a kind of Petri net, and it is possible to construct an equivalent Petri net from this formalism with the same behavior. ...
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What exactly are the classes FP, FNP and TFNP?
In his book Computational Complexity, Papadimitriou defines FNP as follows:
Suppose that $L$ is a language in NP. By Proposition 9.1, there is a polynomial-time decidable, polynomially balanced ...
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Are There Highly Symmetric NP- or P-complete Languages?
Does there exist $L$, an NP- or P-complete language which has some family of symmetry groups $G_n$ (or groupoid, but then the algorithmic questions become more open) acting (in polynomial time) on ...
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Complexity of Computing Lexicographically Minimal Element of Orbit
Given strong generators for a group $(G \leq S_n, *)$ acting on bitstrings of length $n$ and an element $s \in \{0, 1\}^n$, how hard is it to compute the lexicographically minimal element of $G.s$, ...
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Formally proving no algorithm exists [closed]
Are there standard techniques to show that no algorithms exist for given complexity constraints?
For example, consider the following problem. The input is a list of items with exactly one duplicate, ...
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0
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162
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Why does this algorithm not have an exponential complexity? [closed]
In this article :
Kinodynamic Motion Planning
B. Donald, P. Xavier, J. Canny, J. Reif
https://www.cs.duke.edu/brd/papers/src-papers/jacm-final.pdf
The authors present a PTAS algorithm that can ...
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2
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869
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Does Karp reducibility yield a total order?
Or with other words, do we have that for every language $A$ and $B$, $A \leq_p B$ or $B \leq_p A$?
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Equivalence for Constant-width Read-Once Branching Programs with Distinct Orders
Let $X={x_1,...,x_n}$ be a set of variables and $\pi:[n]\rightarrow [n]$ be a permutation of the $n$-element set $[n]=\{1,...,n\}$.
A $\pi$-OBDD is an oblivious, read-once branching program where ...
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