Questions tagged [fixed-parameter-tractable]
algorithms for parameterized problems where the run-time is polynomial in the input size, but depends arbitrarily on the parameter
10
votes
0answers
225 views
Have people looked for parameterized algorithms for problems that are not in NP?
Are there problems that are not in NP (e.g., NEXP-complete problems) but admit FPT algorithms for a reasonable parameterization (and specifically, the standard parameterization of a problem -- the ...
1
vote
0answers
99 views
What definition for $FPT$ algorithm for $KSUM$ gives $W[P]=FPT\implies KSUM$ is $FPT$?
In the definition on $KSUM$ problem we are given $n$ input integers and we have to decide if $K$ of them sum to $0$.
$KSUM$ is $FPT$ if there is a $O(f(K)poly(n))$ algorithm for it. However Downey ...
3
votes
0answers
120 views
What are the consequences if $W[i]=W[i-1]$?
$FPT=W[1]$ does not collapse the $W$ hierarchy however falsifies $ETH$ belief. Is there non-trivial consequence if $W[i]=W[i-1]$ and any other consequence at $W[1]$?
9
votes
4answers
230 views
W[1]-hard problems with FPT time approximation algorithms
I'm looking for problems that are hard to solve in FPT time but has an approximation algorithm. That is, problems that are:
R1. W[1]-hard.
R2. Admit a (preferably constant) approximation algorithm ...
1
vote
1answer
106 views
When we say a parameter is good for a problem?
I am studying parameterized complexity. I have seen few parameterized algorithm for problems like vertex cover, feedback vertex set etc. I have difficulty in determining when a parameter is said to be ...
1
vote
0answers
82 views
Fixed dimension Integer programming minus LLL in fixed parameter $NC$?
If you remove LLL part then is remaining part of
a. Lenstra algorithm
b. Barvinok algorithm
in $O(f(n)(\log(mL))^c)$ time on $O(g(n)(mL)^c)$ processors with fixed $c>0$ in fixed $n$...
1
vote
1answer
161 views
Fixed parameter tractable Integer Programming and $FPP$
Integer programming is $NP$ complete however fixed parameter tractable in number of variables. Is the fixed parameter version in parametrized analogue of $P$-complete or in parametrized analogue of $...
4
votes
1answer
123 views
Is it possible to approximate Maximum Independent Set in $O(2^k\text{poly}(n))$ time?
We know that MIS is hard to approximate within a $n^{1-\epsilon}$ factor in polynomial time and that it is $W[1]$-hard and thus unlikely to admit a $f(k)\text{poly}(n)$ time exact algorithm. (here, $k$...
3
votes
0answers
101 views
Fixed parameter Integer Programming circuit depth complexity
It is well known Lenstra's and Kannan's algorithm achieves $n$-variable parameter $L$-bit integer programming solvability in $O(n^nL)$ time and $O(L)$ space.
If implemented as an arithmetic circuit ...
3
votes
0answers
101 views
Paper regarding the complexity of the longest path problem on weighted directed graphs of bounded treewidth
I would like to cite a paper/report/etc that solves the following problem polynomially in $n$:
Given a weighted directed graph $G=(V,E)$, $|V|=n$, of bounded treewidth $k \in \mathbb{N}$ and a source-...
2
votes
1answer
125 views
Consequences of faster parameterized integer programming
Integer programming in $k$ variables can be done in $k^{O(k)}$ time and $O(k^c)$ space.
Is there any consequence if it can be done in $k^{O(k^\alpha)}$ time and $O(k^c)$ space for some $\alpha\in(0,1)...
6
votes
2answers
316 views
On integer programming
Integer programming is NP-hard.
What is the status of integer programming problem that decides between existence of $\leq1$ solution and $>1$ solutions (note $0$ solutions falls in $\leq1$ ...
7
votes
3answers
496 views
Hard problems for bounded vertex cover
We know that list coloring problem is W[1]-hard when parameterized by vertex cover. Are there any other problems which are also W[1]-hard parameterized by vertex cover?
9
votes
2answers
210 views
Nonstandard dual parametrization of graph problems
One fundamental result in parameterized complexity of graph problems is that VERTEX COVER parameterized by the solution size $k$ is fixed-parameter-tractable (FPT). On the other hand, when ...
5
votes
0answers
78 views
Fixed-parameter tractability of string homomorphism
String homomorphism is a function $h: \Sigma \to \Sigma^*$, which naturally defines a homomorphism on strings from $\Sigma^*$ with respect to concatenation. We denote $H(s) = h(s_1)h(s_2)\dots h(s_n)$ ...
16
votes
0answers
263 views
Complexity of the homomorphism problem parameterized by treewidth
The homomorphism problem $\text{Hom}(\mathcal{G}, \mathcal{H})$ for two
classes $\mathcal{G}$ and $\mathcal{H}$ of graphs is defined as follows:
Input: a graph $G$ in $\mathcal{G}$, a graph $H$ in $...
2
votes
1answer
272 views
What is the best known FPT result for 3-hitting set?
My research problem involves solving a special instance of the 3-Hitting Set problem, and I was wondering whether my result is actually significant (i.e. if it is better than the best known result for ...
-6
votes
3answers
144 views
Fixed parameter tractability [closed]
Lets say I have an algorithm with complexity $O(n^k)$ where $n$ is the size of the input and $k$ is a parameter.
Clearly this is superpolynomial; but in fixed parameter tractability we restrict $k$ to ...
7
votes
2answers
222 views
Parametrized complexity of the 2-Long Paths Problem
Consider the following problem:
Let $G=(V,E)$ be a graph, $s,t\in V$ vertices and $k\in\mathbb N$ an integer parameter. The 2-Long Paths Problems asks whether there exist two disjoint paths from $s$...
10
votes
1answer
259 views
Polynomial kernel for $k$-FLIP SAT on $3$-CNF formulas
The k-FLIP SAT parametrized problem is defined as:
Input: a 3-CNF formula $\varphi$ with $n$ variables and a truth assignment $\sigma : [n] \to \{0,1\}$
Parameter: $k$
Question: can we transform the ...
10
votes
1answer
477 views
Conjecture: All FPT NP-complete languages are fixed-parameter-isomorphic
Berman–Hartmanis conjecture: all NP-complete languages look alike, in the sense that they can be related to each other by polynomial time isomorphisms[1].
I am interested in a more fine-grained ...
15
votes
2answers
761 views
Given a 4-cycle free graph $G$, can we determine if it has a 3-cycle in quadratic time?
The $k$-cycle problem is as follows:
Instance: An undirected graph $G$ with $n$ vertices and up to $n \choose 2$ edges.
Question: Does there exist a (proper) $k$-cycle in $G$?
Background: For any ...
6
votes
1answer
274 views
Complexity of k-clique for hypergraphs
Classic Problem:
Let a number $k$ be given. The $k$-clique problem is as follows.
Given a graph $G$, does there exist a subset $S$ of $k$ vertices so that any two vertices of $S$ are adjacent?
...
-1
votes
1answer
121 views
FPT algorithm equivalent definitions [closed]
On this page, the definition of a Fixed-Parameter Tractable algorithm is given, followed by the very classical example, Vertex Cover.
But how the complexity given for Vertex Cover, $O(kn+1.274^k)$ (...
1
vote
1answer
134 views
Natural maximization problems in FPT
Is there a natural (and hopefully well-known) maximization problem that is known to be in FPT?
For instance, Vertex Cover is in FPT, but it's a minimization problem.
I'm looking for natural ...
6
votes
1answer
214 views
Easy decision hard counting Parametrized
It is known that counting perfect matchings in a bipartite graph is #P-complete. On the other hand, finding a perfect matching belongs in P.
Is there a problem, that exhibits the same behavior in ...
8
votes
2answers
458 views
Implications of a problem being in XP when parameterized by diameter
Let $X$ be an NP-complete graph problem. Suppose $X$ is solvable in polynomial time on graphs of bounded diameter. In other words, $X$ parameterized by diameter is in XP. (Recall a problem is in XP if ...
3
votes
0answers
105 views
Multiple knapsack fpt?
It was an open question whether multiple knapsack is fpt wrt standard
parameter. Since at SODA 2009 Jansen has presented an EPTAS for
multiple knapsack and an EPTAS implies the existense of an fpt ...
7
votes
0answers
144 views
Is 4-colors precoloring extension for planar graphs fixed parameter tractable?
Given a planar graph $G=(V,E)$, there exists a quadratic algorithms for 4-coloring $G$ (and $G$ is surely 4-colorable).
Assume you are given a set of $k$ constraints of the form "$v_i \text{ is ...
10
votes
2answers
333 views
Which graph problems are $W[1]$-Hard on directed(/weighted) graphs but FPT on undirected(/unweighted) graphs?
Following the equivalent questions regarding NP-Completeness (see the weight question and the directed question), I was wondering how parameterized problems are affected by these attributes.
...
4
votes
1answer
334 views
FPT algorithm for mixed integer program
It is known that every integer linear program parameterized by the number of variables is FPT (fixed parameter tractable). Is every mixed integer program parameterized by the number of integer ...
1
vote
1answer
91 views
Connecting vertices after struction operation in J.Chen, I.Kanj, G.Xia vertex cover algorithm
EDIT: I'm sorry if this question belongs more to cs.SE, I've had a dilemma about where to put it. Please let me know if it's inappropriate.
I'm currently implementing the Vertex Cover problem solving ...
7
votes
2answers
198 views
Is it known whether counting $q$-dimensional $p$-matching is $\#W[1]$-Hard?
The $q$-Dimensional $p$-Matching is defined as follows:
Given disjoint universes $U_1,\ldots,U_q$, think
of an element in $U_1\times\ldots\times U_q$ as a set that contains exactly one element
from ...
1
vote
1answer
198 views
Node-weighted steiner problem with few terminals
Consider the node-weighted steiner problem:
Input: a graph $G=(V,E)$, a set $T\subseteq V$ of terminals, a weight function $w: V\setminus T \to \mathbb{R}_+$.
Output: a minimum weight subset ...
5
votes
0answers
121 views
Is minimum weight simple cycles through specified vertics fixed parameter tractable?
The problem formulation is as follows:
Input: Undirected graph $G=(V,E)$, a set of vertices $S\subseteq |V|$, a weight function $w:E\to \mathbb{R}$ and a threshold $T\in \mathbb{R}$.
Parameter:...
4
votes
1answer
312 views
Vertex disjoint simple paths of length k
A lot of effort has been invested in finding simple k-paths, as well as in finding vertex disjoint paths.
Is there any known parametrized algorithm that given a graph $G=(V,E)$, decides whether there ...
15
votes
1answer
181 views
Clique-width expressions with logarithmic depth
When we are given a tree decomposition of a graph $G$ with width $w$, there are several ways in which we can make it "nice". In particular, it is known that it is possible to transform it into a tree ...
18
votes
4answers
998 views
Open problems related to Graph isomorphism
Presently I am doing literature survey on Graph isomorphism (GI) problem.
I would like to know some open questions related to the following
What are the graph parameters for which fixed parameter ...
4
votes
1answer
467 views
On Random Self-reducible properties
Permanent is random self-reducible. $\mathsf{SAT}$ is not random self-reducible since otherwise the polynomial hierarchy collapses to $\mathsf{\Sigma_3}$.
1) Is $k$-sum random self-reducible?
That ...
14
votes
5answers
880 views
Exact Algorithms for r-Dominating Set on Bounded Treewidth Graphs
Given a graph, $G = (V, E)$, I want to find an optimal $r$-domination for $G$. That is, I want a subset $S$ of $V$ such that all vertices in $G$ are at a distance of at most $r$ from some vertex in $S$...
13
votes
7answers
1k views
Books/Lecture Notes on Parametrized Complexity
I would like to learn about Parametrized Complexity (both on the algorithmic side and on the hardness side). What books/lecture notes can I read on this subject?
10
votes
1answer
343 views
What is the motivation behind the definition of fixed parameter tractability?
Wikipedia writes:
FPT contains the fixed parameter tractable problems, which are those
that can be solved in time $f(k)\cdot|x|^{O(1)}$ for some computable function $f$. Typically,
this ...
7
votes
3answers
482 views
Algebraic formulation for packing problem
My question is regarding the algebraic formulation for packing problems in graphs.
Taking an example, suppose I am interested in the problem of finding if there is a packing of k edge disjoint ...
2
votes
1answer
229 views
Complement problems are not in the same class in parametrized complexity hierarchy? If not in $P$
By "complement problems", I mean the two problems' objective functions are complement. For example, the vertex cover and its complement independent set in this sense. For a graph $G(V,E)$, their ...
7
votes
2answers
454 views
Variants of Cluster-Vertex-Deletion problem
The Unweighted Cluster-Vertex-Deletion problem is the following:
Input: An undirected graph G = (V, E) and a nonnegative number k
Output: Is there a subset X ⊆ V with |X| ≤ k such that deleting all ...
13
votes
1answer
239 views
Elementary bounds on parameter in fixed-parameter tractability?
In the definition of (strong) fixed-parameter tractability, the time bound is an expression of the form $$f(k).p(|x|),$$ where the input instance is $(x,k)$ with parameter $k$, $p$ is a polynomial, ...
18
votes
1answer
480 views
FPT vs W[P] - Parameterized Complexity
In parametrized complexity, $\mathsf{FPT} \subseteq \mathsf{W}[1]$ $\subseteq \mathsf{W}[2]$ $\subseteq \ldots \subseteq \mathsf{W}[P]$. It is conjectured that each of the containments is proper.
If $...
12
votes
1answer
263 views
Any results on binary boolean CSP beyond the fixed-parameter tractability of almost 2SAT problem?
Let $\varphi$ be a 2CNF formula and $k$ a nonnegative integer. It is proved in this paper that the problem of deciding whether one can delete at most $k$ clauses to make $\varphi$ satisfable, is fixed-...
13
votes
2answers
915 views
Relation between fixed parameter and approximation algorithm
Fixed parameter and approximation are totally different approaches to solve hard problems. They have different motivation. Approximation looks for faster result with approximate solution. Fixed ...
13
votes
5answers
721 views
Hardness of FPT problems
Vertex Cover can be easily reduced to Independent Set and vice versa.
However, in the context of parameterized complexity, Independent set is harder than Vertex Cover. A kernel with $2k$ vertices ...
