Skip to main content

Questions tagged [submodularity]

In mathematics, submodular functions are set functions which usually appear in approximation algorithms, functions modeling user preferences in game theory,economics, combinatorial optimization, electrical networks and operations research.

Filter by
Sorted by
Tagged with
1 vote
1 answer
109 views

A variant of the generalised assignment problem

I am trying to solve this problem: There are $N$ workers and $T$ tasks. Each task can be assigned to at most one worker. Each worker can be assigned any number of tasks. The profit obtained by ...
Michael C.'s user avatar
3 votes
0 answers
48 views

Approximate decomposition of a many-to-one assignment

Suppose we have $n$ items and $n$ agents and we want to assign one item to each agent. We have a probability matrix $P$ such that $p_{i,j}$ is the probability that agent $i$ gets item $j$. If $\sum_j ...
Erel Segal-Halevi's user avatar
2 votes
0 answers
81 views

Submodular function minimization over integer lattice

Let $[k]=\{0,1,\ldots,k-1\}$. A function $f:[k]^n\to \mathbb{R}$ is submodular if $f(x)+f(y)\geq f(\max(x,y))+f(\min(x,y))$ for all $x,y\in [k]^n$. Here $\max$ and $\min$ are applied coordinate-wise. ...
Chao Xu's user avatar
  • 4,479
4 votes
0 answers
83 views

Submodular welfare maximization: what is the best known approximation ratio of a deterministic algorithm?

In the submodular welfare maximization problem, there is a set $M$ of items that should be partitioned among $n$ agents. Each agent $i$ has a value function $v_i: 2^M\to \mathbb{R}_+$. All value ...
Erel Segal-Halevi's user avatar
1 vote
1 answer
82 views

A bound that follows from submodularity

I am studying Lemma 1 of this paper: The Adaptive Complexity of Maximizing a Submodular Function. The proof appears on page 11. I got stuck on this inequality: where $f$ is a monotone submodular set ...
Null_Space's user avatar
4 votes
1 answer
196 views

Restriction of a convex function to {0, 1}^n

Suppose I have a real-valued convex function $f$ on the unit hypercube $[0,1]^n$, and let $\bar{f}$ be its restriction to the integer points $\{0,1\}^n$. Does $\bar{f}$ satisfy any properties, or can ...
Sean L.'s user avatar
  • 43
1 vote
0 answers
58 views

Tight estimates on the Lovász and Multilinear extensions of a submodular function

I assume here some familiarity with the jargon used in submodular optimization (please let me know if something is unclear). Let $f:2^V \to \mathbb{R}$ be monotone, normalized and submodular. For ...
MathematicsStudent1122's user avatar
2 votes
1 answer
196 views

Reference request --- minimizing a non-increasing submodular function with (upper bound) cardinality constraint

Suppose a set function $f(S)$ is submodular and non-increasing, meaning that for any $S'\subset S$, $f(S') \geq f(S)$. The problem is to minimize $f(S)$ s.t. $|S| \leq k$. I am wondering if there are ...
Paradox's user avatar
  • 121
1 vote
1 answer
268 views

Minimizing SubModular Function: Cardinality

Given a submodular function f: 2^V to reals (not necessarily monotone), and an integer k, find a set S such that |S| <= k and such that f(S) is minimized. When the size constraint is |S| >=k, the ...
Pavan Aduri's user avatar
3 votes
0 answers
47 views

Approximating a monotone submodular function using a concrete coverage function

Is it possible to approximate a monotone submodular function using a concrete coverage function, i.e. Given a ground set $U$ and a monotone submodular function, $f:2^U\to \mathbb{R}$, the goal is to ...
Gilad's user avatar
  • 143
1 vote
1 answer
304 views

Monotone supermodular function minimization under partition matroid constraints

Is there a known approximation algorithm for the problem of minimizing a monotone (non increasing) supermodular function under partition matroid constraints ?
Gilad's user avatar
  • 143
2 votes
0 answers
90 views

On the impossibility of representing/approximating subadditive function using additive functions

I am trying to understand whether a monotone and subadditive function $f(S), S \subseteq 2^{[n]}$ and $ f : 2^{[n]} \rightarrow R_{\geq0}$ can be represented using an additive function $\hat{f}(S) = \...
karmanaut's user avatar
  • 1,177
11 votes
0 answers
372 views

Extreme rays of the cone of submodular functions

Consider a ground set $U=\{1,2,...,n\}$ and the set $\mathcal{F}$ of all non-negative submodular functions $f: 2^U \mapsto \mathbb{R}_{\geq 0}$. The set $\mathcal{F}$ is closed under taking linear ...
Marek Adamczyk's user avatar
6 votes
1 answer
193 views

Minimizing entropy plus a modular function

I have a question about whether there are faster algorithms for specific submodular minimization problems. In particular, I am trying to find a fast algorithm for minimizing the following set ...
Asterix's user avatar
  • 617
1 vote
0 answers
288 views

Maximize the weight of MST + sum of vertex weights

I am considering a problem where the goal is to choose a subset of size $k$ of the vertices in a graph, such that the weight of their minimum spanning tree + the sum of their vertex weights is ...
Johnson's user avatar
  • 19
1 vote
1 answer
96 views

Properties of convex polytope of 0-1 matrices

Problem setting Consider a set $ S = \big\{ 1,2,\cdots,n \big\}$. Now consider $k$ equal-sized subsets $S_i \subset S$ s.t of size $\big|S_i\big|=n' \;\forall i$. Consider a $k\times k$ matrix $M$ ...
Vivek Bagaria's user avatar
5 votes
1 answer
242 views

Minimizing a submodular function given noisy oracle access

Let $f\colon 2^{[n]} \to \mathbb{R}$ be a submodular function (one can assume $f$ is bounded, if this helps). We are given noisy oracle access to $f$: on any $S$ and for any $\tau > 0$, one can ...
Clement C.'s user avatar
  • 4,471
8 votes
0 answers
232 views

NP-hardness of approximation for unconstrained submodular maximization

The problem of unconstrained submodular maximization can be phrased as follows: Given a non-negative submodular function $f$ on a domain $D$ find a set $S \subseteq D$ maximizing $f(S)$. Here a ...
Yuval Filmus's user avatar
  • 14.5k
10 votes
1 answer
1k views

Maximum weight matching and submodular functions

Given a bipartite graph $G = (U \cup V, E)$ with positive weights let $f: 2^U \rightarrow \mathbb{R}$ with $f(S)$ equal to the maximum weight matching in the graph $G[S\cup V]$. Is it true that $f$ ...
George Octavian Rabanca's user avatar
4 votes
1 answer
2k views

Maximizing a monotone supermodular function s.t. cardinality

I've tried to comb the literature and seen a lot of references to results that almost but don't quite seem to address this. Question: Is it known to be true or is there a hardness result ...
usul's user avatar
  • 7,615
4 votes
0 answers
1k views

Minimizing a monotone submodular function under a cardinality constraint

I would like to know what the status of the following question is: Given query access to a non-decreasing, non-negative submodular function $f\colon 2^{[n]} \to \mathbb{R}$ and a parameter $0 \leq ...
Clement C.'s user avatar
  • 4,471
3 votes
1 answer
213 views

A maximization problem containing summation and multiplication

Are the following two problems NP-hard? Problem 1 Given $n$ ordered pairs of integers $S=\{(a_i,b_i)\}$, $1\leq i \leq n$, and an integer $k$. Find a subset $A$ of $S$ with $k$ elements, such that $...
Arthur's user avatar
  • 107
0 votes
0 answers
133 views

Maximize number of bins and minimize cost of elements chosen from a set

I am considering the following problem: there is a set of elements $S$ where each element is assigned to a bin $B$. The bins are disjoint and their union is $S$. There is also a cost function ...
eagle34's user avatar
  • 101
2 votes
1 answer
269 views

When can a convex function induce submodularity?

Say I have a real valued convex function $f$ on the hypercube $[-1,1]^n$. Let $f'$ be the induced function on the discrete hypercube $\{-1,1\}^n$. Now I want to find a vertex on $\{-1,1\}^n$ on which ...
Student's user avatar
  • 654
5 votes
1 answer
141 views

How to sample from a distribution with submodular weights

Is there a known algorithm for sampling a set $S \subset \{1,...,n\}$ with probability $p_S = \frac{e^{f(S)}}{\sum_{T \subset \{1,...,n\}} e^{f(T)}}$ where $f: 2^{\{1,...,n\}} \to \mathbb{R}$ is a ...
Asterix's user avatar
  • 617
1 vote
0 answers
605 views

Hardness of Minimizing Submodular Functions with Cardinality Constraints

I am new to submodular functions and I am reading the introductions to submodular functions and applications ( https://www.ima.umn.edu/optimization/seminar/queyranne.pdf ). In this introduction, it ...
Jerry Song's user avatar
7 votes
1 answer
504 views

Are there any interesting open questions having to do with submodularity, specially in the intersection of theoretical machine learning?

I was interested in knowing about open research topics related with sub modularity, specially within its intersection with theoretical machine learning (and related topics). I am particularly ...
Charlie Parker's user avatar
5 votes
0 answers
113 views

Maximizing a submodular function with restricted values

Maximizing a general monotone submodular function $f$ under the constraint that $|S|\leq k$, can be approximated to $(1-1/e)$. I am wondering if a better approximation algorithm exists if the ...
George Octavian Rabanca's user avatar
2 votes
0 answers
89 views

Name for the "stronger submodularity" property in cut function

Let $f:2^V \rightarrow \mathbb{R}$ be a set function over $V$ that satisfies the following: $f(A \cap B) + f(A \cup B) \le f(A) + f(B)$ $f(A \backslash B) + f(B \backslash A) \le f(A) + f(B)$. ...
Thatchaphol's user avatar
  • 1,130
4 votes
0 answers
207 views

Submodular function re-optimization (after an update)

The problem I have is as follows: I know the minimizer/minimum of a non-negative submodular function, and want to use this to efficiently compute the minimizer/minimum of a "perturbed" submodular ...
rk2's user avatar
  • 171
8 votes
1 answer
334 views

Maximizing a submodular function of two sets with different size constraints

I have two totally distinct domains (apples and oranges) and I have a function $f$ that takes a set of objects from the first domain and a set of objects from the second domain and returns a real ...
Francesco Bonchi's user avatar
6 votes
2 answers
928 views

Maximizing difference of a submodular and a modular function

I'm considering a network planning problem which is stated as follows: From the given ground set $\mathcal{V}$, select $\mathcal{A} \subseteq \mathcal{V}$ such that \begin{equation} f(\mathcal{A}) - \...
Ali's user avatar
  • 61
4 votes
0 answers
185 views

Term rewriting for proving inequalities

Suppose $f$ is a submodular set function on a universe $U$ of size $n$. For $k \in \{0,\ldots,n\}$, let $$ F(k) = \operatorname*{\mathbb{E}}_{X \in \binom{U}{k}} f(X), $$ where $\binom{U}{k}$ is the ...
Yuval Filmus's user avatar
  • 14.5k
13 votes
2 answers
376 views

Strengthenings of submodularity

A set-function $f$ is monotone submodular if for all $A,B$, $$ f(A) + f(B) \geq f(A \cup B) + f(A \cap B). $$ A stronger property is $$ \begin{multline*} f(A) + f(B) + f(C) + f(A\cup B\cup C) \geq \\...
Yuval Filmus's user avatar
  • 14.5k
9 votes
1 answer
380 views

Decomposing a submodular function

Given a submodular function $f$ on $\Omega=X_1\cup X_2$ where $X_1$ and $X_2$ are disjoint and $f(S)=f_1(S\cap X_1)+f_2(S\cap X_2)$. Here $f_1$ and $f_2$ are submodular on $X_1$ and $X_2$ respectively....
Ashwinkumar B V's user avatar