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Questions tagged [optimization]

general questions about selecting a best element from some set of available alternatives.

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24 views

Which matrix of Q values is being used here?

This question refers to this paper: Using Free Energies to Represent Q-values in a Multiagent Reinforcement Learning Task In section 2.1, equations (5) and (6), I am wondering which Q values are ...
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0answers
154 views

NP-hardness of minimizing sum of complicated objective function

In our research, we faced the following problem optimization problem: Input: a list of $k$ pairs of positive integers $(n_1,d_1), \ldots, (n_k,d_k)$; an integer $m$. Output: $P$, a partition of the ...
4
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1answer
85 views

Approximate matching in table of integer vectors

Disclaimer: This is my first question on cstheory.stackexchange.com so please be forgiving. I have a list of M (M is big, more than 1 million elements) vectors of integers. Each vector can contain 0-...
4
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1answer
178 views

What do you call the join of two optimization problems?

I have two optimization problems, both of whose inputs are from the set $I$ and whose solutions are from the set $S$, one a minimization with objective function $m_{\min}$ and one a maximization with ...
4
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1answer
205 views

Minimum weight matching in general graphs with additional input specifying the number of matched edges

We know of the minimum weight perfect matching problem in general graphs which can be solved using a primal-dual algorithm. Assume, we have an additional constraint specifying the exact number of ...
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2answers
2k views

Finding the two shortest paths while minimizing the number of nearby/common edges

The shortest path problem between 2 arbitrary nodes is one that has been covered extensively and the solution is well-known. Consider the edge costs to be arbitrary. Consider the following variant: ...
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0answers
119 views

Completing a matrix (over the reals) to be singular

Consider the following problem: you are given a matrix (say, with rational entries) some of whose entries are actually left blank; can these blanks be filled in with real numbers so that the resulting ...
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2answers
255 views

What are some of the most ingenious linear programs developed for tackling hard combinatorial problems?

What are some known ingenious linear programs that have been developed for tackling hard combinatorial optimization problems, especially any linear programs which had helped in getting good ...
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0answers
186 views

NP-hardness of a quadratic programming problem

Motivated by the mean-variance optimization, I came up with the following question: Given $n$ integers $a_1, \cdots, a_n$; $n$ lower bounds $0<\ell_1, \cdots, \ell_n<1$ $n$ upper bounds $0<...
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2answers
454 views

Finding a set of hubs in a graph

Suppose, we are given a graph $G = (V,E,d)$, where $V$ is the set of vertices, $E$ is the set of edges, and $d$ is a distance function $d: E \mapsto \mathbb{R^+}$. Let $S$ be the set of source ...
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1answer
230 views

NP-Hardness for an optimization problem

I want to prove that the following optimization problem is NP-Hard. max $\prod_{i = 1}^{N} \frac{\left[\sum_{j =1}^M x_j \mathcal{R}_{ij}\right]^2}{ \sum_{j=1}^M x_j}$ subject to $x_j \in \{0,1\}\...
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1answer
134 views

TSP heuristics for limited distance information

this is my first question on Theoretical CS. :) I've posted a similiar question on Mathoverflow and a friendly user advised me to post my question on this site. Problem: I'm looking for TSP ...
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0answers
296 views

How good is greedy in average?

Given a family ${\cal F}\subset 2^E$ of (feasible solutions), the maximization problem on ${\cal F}$ is, for every weighting $x:E\to \{0,1,\ldots\}$ of ground elements, to compute the maximum weight ...
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718 views

How to solve such a graph optimization problem?

I have a graph optimization problem which is hard to describe in the title. There is a component based system which consists of components and data transmissions between components(components and ...
5
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1answer
139 views

Is computing the dual optimum of a degenerate LP equivalent in complexity to solving LP?

Given a primal LP and an optimum solution thereof, it is well-known that complementary slackness conditions [1] can be used in non-degenerate cases to produce a dual optimum solution. For instance, ...
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1answer
652 views

Complexity: simulated annealing vs. quantum annealing

How do I compare the performance of simulated annealing against the performance of quantum annealing algorithms? In Convergence theorems for quantum annealing by Morita and Nishimori, it has been ...
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0answers
215 views

Dynamical systems analysis of deep learning

I am interested in finding out references that apply dynamical systems analysis to develop the "theory" of deep learning, specifically (say) feedforward deep neural nets. The only paper I seem to have ...
13
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1answer
339 views

Second Smallest $s$-$t$-Cut in a Network

Is anything known about the second smallest $s$-$t$-cut in a flow network? Or, more general, about this problem: Input: A network $N$ and a number $k$, all in binary. Output: A $k$th smallest $s$-...
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1answer
346 views

Is the complexity of this covering problem known?

Let $G=(V,E)$ be a graph. A vertex set $X\subseteq V$ is called critical if $X\neq\emptyset$ and no vertex in $V\setminus X$ is adjacent to exactly one vertex in $X$. The problem is to find a vertex ...
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5answers
5k views

Is it a rule that discrete problems are NP-hard and continuous problems are not?

In my computer science education, I increasingly notice that most discrete problems are NP-complete (at least), whereas optimizing continuous problems is almost always easily achievable, usually ...
13
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2answers
551 views

Numerical precision in sum-of-squares method?

I have been reading a bit about the sum-of-squares method (SOS) from the survey of Barak & Steurer and the lecture notes of Barak. In both cases they sweep issues of numerical accuracy under the ...
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2answers
306 views

Reordering data to optimize for compression?

Are there any algorithms for reordering data to optimize for compression? I understand this is specific to the data and the compression algorithm, but is there a word for this topic? Where can I ...
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0answers
111 views

Optimizing over symmetric polynomials [closed]

Consider the following constraint satisfaction problem: Let $\alpha_1 , \ldots, \alpha_k \in \mathbb{R}$ be given as well as an error parameter $\epsilon$. Find $p_1, \ldots, p_n$ such that (i) $0 \...
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2answers
994 views

Good algorithms to solve ATSP

What are some good neighborhood-based local search algorithms or strategies to solve the Asymmetric TSP ? I see many 2-OPT and K-opt based algorithms (e.g. Lin-Kernighan implementations), but I think ...
2
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1answer
116 views

Is there a name for this Assignment definition

The standard Assignment Problem asks for an optimal one-to-one assignment between agents and tasks. Now consider the following generalization: Instead of specifying a cost of a single agent-task ...
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0answers
113 views

What is the most “unbalanced” vector between two given vectors of numbers?

Let $\mathbb{R}_+$ be the set of non-negative real numbers. Let $m$ be a positive integer and $\leq_m$ the product ordering on $\mathbb{R}_+^m$. That is, $\leq_m$ is the partial ordering on $\mathbb{R}...
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198 views

Steiner Tree and minimum spanning tree

If I must connect: $$2^k$$ terminals in a Steiner Tree choosen randomly and connect them with the cheapest component; "loss - contracting algorithm" is a good way? Or is an "Iterative Randomized ...
4
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1answer
190 views

minimal finite automata given in-words and out-words

this seems an interesting FSM optimization problem; have not seen it studied, wondering if it has been and/ or looking for other insight. given: two finite sets of words $S_{in}$ and $S_{out}$. ...
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0answers
87 views

Approximation Algorithm for TSP-like problem

Suppose we are given a graph with distances for each of the edges and merit for each of the nodes. What are the best (approximation) algorithms for computing the the most meritorious simple path with ...
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0answers
291 views

Follow the Perturbed Leader for nonlinear cost functions

The famous FTPL algorithm [1] is analyzing linear cost function. Is there any generalized proof for nonlinear functions known? Note that in the last paragraph of [1] it says "It would be great to ...
1
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1answer
325 views

direct connection between gradient descent and follow the (perturbed) leader algorithm or weighted majority?

Is there a direct conversion between gradient descent ([1], Alg 1 ) and any of the following algorithms? 1) Weighted Majority: http://onlineprediction.net/?n=Main.WeightedMajorityAlgorithm 2) ...
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2answers
135 views

Finding the paths through a graph that reuse as many of the nodes as possible

I'm implementing an encryption algorithm which does a bunch xor operations to mix up the columns. Because I want to find the lower bound of the number of ...
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2answers
245 views

Minimal cumulative set sum

Consider this problem: Given a list of finite sets, find an ordering $s_1, s_2, s_3, \ldots$ that minimizes $|s_1| + |s_1 \cup s_2| + |s_1 \cup s_2 \cup s_3| + \ldots$. Are there known algorithms ...
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1answer
288 views

What is the state of the art in cache algorithm theory?

I recently became interested in the general problem of optimizing memory usage in a situation where there is more than one kind of memory available, and there is a trade-off between the capacity of a ...
4
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1answer
267 views

Approximation algorithms for min vector subset-sum over GF(2)

In this question vzn asked about the following problem, which I'll call Vector-Subset-Sum. Given a set of vectors $v_i$ over GF(2) and a target vector $y$, is there a subset of the $v_i$ summing to ...
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1answer
154 views

Finding optimal subset for quadratic function

Given a set of $n$ elements $e_1,...e_n$ where each element $i$ is associated with two positive integers $\alpha_i$ and $\beta_i$. Given another integer $\lambda$, the goal is to find a set $S$ of ...
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2answers
681 views

What is this variant of set cover problem known as?

Input is a universe $U$ and a family of subsets of $U$, say, ${\cal F} \subseteq 2^U$. We assume that the subsets in ${\cal F}$ can cover $U$, i.e., $\bigcup_{E\in {\cal F}}E=U$. An incremental ...
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0answers
378 views

lower bound for difference between max cut and min cut

Let $G=(V,E)$ be a graph on $n$ vertices with edge weights $w=(w_e)_{e\in E}$. Let $M^+$ and $M^-$ be the maximum and the minimum cut values, i.e. $$M^+=\max\limits_{(U_1,U_2)}\left\{\sum_{e=\{u,v\}\...
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0answers
213 views

Dynamic Programming with two optimization goals

I am working on the problem of distributed database query planning. Existing work [1] uses dynamic programming to search the potential query plan space and find the one with minimal cost. However, I ...
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1answer
1k views

exact cover set problem

i am searching an heuristic algorithm for a weighted exact cover problem shown here: http://en.wikipedia.org/wiki/Exact_cover On my research i only found algorithm which calculates all solutions ...
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1answer
1k views

Fast algorithm for weighted bipartite matching problem

I have a set of $n$ agents and a set of $n$ tasks, and I need to assign each agent to exactly one task such that a cost is minimised. Some agents are incompatible with some tasks. I have an ...
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0answers
109 views

Computing the most likely winner in elections : intermediate case between Kemeny and Borda?

Given $n$ possible alternatives satisfying some unknown linear ordering, a multiset of pairwise votes, i.e., a matrix $M\in\mathbb{N}^{n\times n}$: $M_{i,j}$ counts the number of votes for which $i&...
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0answers
95 views

LP solver for sparse, PSD and strictly diagonally dominant matrix

I have a linear problem with a sparse, psd and strictly diagonally dominant matrix. Can you please point me to some known best solvers (in terms of runtime, or easy to be practically optimized for ...
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0answers
246 views

NP-hardness of tasks graph assignment to two heterogenous servers

I have a problem with determinig if the following assignment problem is NP-hard. Any comments and suggestions would be appreciated. Problem definition Given is a directed acyclic graph $G=(V,E)$ ...
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0answers
199 views

Automatically Adapting Forgetting Factor for Online EM

I've been reading some interesting papers recently on methods for automatically and adaptively setting the learning rate in stochastic gradient descent (SGD). In particular, "No more pesky learning ...
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0answers
91 views

Linear ordering of bipartite tournament graphs

I have an ordered bipartite graph such that every node of the first node set is connected to every node in the second node set by an edge of a given direction (i.e., a so-called bipartite tournament ...
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0answers
68 views

Proof of convergence of alternative minimization/maximization [duplicate]

Given a problem \begin{equation} \max_{x\in X} \min_{y \in Y} f(x,y) \end{equation} where $f$ is strongly convex in $Y$ and strongly concave in $X$ How to show that the following iterative ...
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2answers
202 views

Iteratively minimizing the function

Consider the problem \begin{equation} \min_{x\in X, y \in Y} f(x,y) \end{equation} Can I solve the problem by iteratively solving the following two sub problems? \begin{equation} x_{k+1} = \arg\...
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0answers
58 views

arithmetic formula simplication

Consider a function $f : \mathbb R^m \rightarrow \mathbb R^n$. Function $f$ can be written down as a simple arithmetic program. It uses addition, subtraction, multiplication and division - however, ...
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3answers
549 views

Is it possible to optimize the calculation of $ax+b$ once I know $a$ and $b$?

An "algorithm" for calculating $ax+b$ would take the steps Calculate $a$ times $x$ Calculate $b$ plus the result of previous line. But if the values of $a$ and $b$ are known, can we create a more ...