# Questions tagged [partial-order]

A partial order is a binary relation over a set which is reflexive, antisymmetric, and transitive.

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### Time complexity of finding chain decomposition of partially ordered set

Given a partially ordered set $P$ with $n=|P|$ and width $w$: -What is the best known complexity (in expectation) for finding a chain decomposition of $w$ chains? -What is the best known complexity (...
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### Jump number approximation algorithm

A linear extension $x_1 x_2 \ldots x_n$ of a partially ordered set (poset) is said to have $k$ jumps if there are $k$ occurrences of consecutive elements that are incomparable with each other -- i.e., ...
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### How to prove that Supremum preorder coincides with Hoare preorder?

Given a complete lattice $(L, \sqsubseteq)$ and a basis of completely $\sqcup$-irreducibles $B_L \subseteq L$, such that $\forall l \in L$, $l=\sqcup\{b \in B_L\ |\ b \sqsubseteq l\}$. I mean: Hoare ...
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### Positive topological ordering

Suppose I have a directed acyclic graph with real-number weights on its vertices. I want to find a topological ordering of the DAG in which, for every prefix of the topological ordering, the sum of ...
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### Computing topological sort while keeping edges “short”

Motivation: I want to compute a topological sort order in which the connected vertices are close to each other. Problem statement: Given a DAG $G(V,E)$ with $n$ vertices, compute a topological sort ...
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### Enumerating topological sorts of a vertex-labeled DAG

Let $G = (V, E)$ be a directed acyclic graph, and let $\lambda$ be a labeling function mapping each vertex $v \in V$ to a label $\lambda(v)$ in some finite alphabet $L$. Writing $n := |V|$, a ...
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### Complexity of topological sort with constrained positions

I am given as input a DAG $G$ of $n$ vertices where each vertex $x$ is additionally labeled with some $S(x) \subseteq \{1, \ldots, n\}$. A topological sort of $G$ is a bijection $f$ from the vertices ...
184 views

### NP-completeness of a specific topological sorting problem

Consider $(V, E)$ be a DAG, and $p_1, \dots, p_n$ be its topological sorting (i.e. such permutation $p$ of $V$ that $\forall(x, y) \in E.\ p^{-1}(x) < p^{-1}(y)$). Let's call the goodness of $p$ a ...
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### Lighting up all elements of a poset by toggling upsets

I consider the following game on a finite poset $(P, <)$. At each point of the game, I have a set of elements $S$ of the poset which are "on", and all others are "off". Initially $S = \emptyset$. ...
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### Meet of integer partitions

An integer partition of $n$, $A$, is a multiset of positive integers such that $\sum_{a \in A} a= n$. We say that $B \leq A$, if there exists a map $\phi: |B| \to |A|$, such that for $a \in A$, we ...
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### Is the isomorphism problem between posets represented by DAGs GI-complete?

Given two directed acyclic graphs, how hard is the problem of checking whether the partial orders they represent are isomorphic? Is this problem GI-complete? I believe this problem is equivalent to ...
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### Lattice problems

There has been a fair amount of work on computational problems for partial orders (e.g., recognition, jump number, comparability graph recognition, etc...). I am curious what work specific to ...
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### The originator of the fixed point theorem for DCPOs

Pataraia proved in "A constructive proof of Tarski’s fixed-point theorem for dcpo's", presented in the 65th Peripatetic Seminar on Sheaves and Logic, in Aarhus, Denmark, November 1997 that in a ...
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### Determining what can be achieved by a permutation of elements of a noncommutative group

Fix a finite group $G$. I am interested in the following decision problem: the input is some elements of $G$ with a partial order on them, and the question is whether there is a permutation of the ...
338 views

### Generalization of Dilworth's theorem for labeled DAGs

An antichain in a DAG $(V, E)$ is a subset $A \subseteq V$ of vertices that are pairwise unreachable, namely, there are no $v \neq v' \in A$ such that $v$ is reachable from $v'$ in $E$. From Dilworth'...
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### Series-parallel extension of a partial order respecting a given total order

Consider a partial order $P$, a series-parallel order $Q$ and a total order $R$, such that $P \subseteq Q \subseteq R$. Given $P$ and $R$, we are asked to find $Q$ of minimum length. An $O(n^3)$ ...
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### Generalizing linear interpolation to posets

Assume that I have an array $A$ of $n$ numerical values where some are known and some are unknown (with $A$ and $A[n-1]$ assumed to be known). If I want to estimate an unknown value $A[i]$, a ...
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### Compatible partial permutations

Please, correct my terminology as I am not a combinatorician (I am using http://en.wikipedia.org/wiki/Partial_permutation). Please, refer me to the solution if this is a solved problem. Let $P_k$ be ...
331 views

### Linear ordering from weighted directed graph (kittens)

I want to build a website to find the cutest kitten(TM) there is. People can upload photos of their kittens, but also can vote on which kitten is the cutest. However, I don't want them to rate on a 1 ...
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### How to find the set of edges for the directed graph associated with a partial order?

I have a set $S$, and a partial order relation $\preceq$ defined on $S$. The way this partial order is given to me is through a function $f:S\times S \to \{true, false\}$, where $f(a,b) = true$ if ...
357 views

### Verifying consistency of strict and non-strict partial orders constraints

I am building a set of constraints of the kind $x < y$ and $x \leq y$, where $<$ is a strict order and $\leq$ is a non-strict order on the same set, and $x$ and $y$ are abstract variables ...
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### Efficient representation of set of partial order

I guess that notions I describe are already well known, may be by combinatorician, but I do not know their name or any book/article about them. So if you have a link/title I would love to read it. ...
399 views

### Worst number of questions needed to learn a monotonic predicate over a poset

Consider $(X, \leq)$ a finite poset over $n$ items, and $P$ an unknown monotonic predicate over $X$ (i.e., for any $x$, $y \in X$, if $P(x)$ and $x \leq y$ then $P(y)$). I can evaluate $P$ by ...
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### Minimal elements of a monotonic predicate over the powerset $2^{|n|}$

Consider a monotonic predicate $P$ over the powerset $2^{|n|}$ (ordered by inclusion). By "monotonic" I mean: $\forall x, y \in 2^{|n|}$ such that $x \subset y$, if $P(x)$ then $P(y)$. I am looking ...
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### Binary search generalizations for posets?

Suppose I have a poset "S" and a monotonic predicate "P" on S. I want to find one or all maximal elements of S satisfying P. EDIT: I'm interested in minimizing the number of evaluations of P. What ...
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### Partially Ordered CFG

I'm looking for work about partially ordered context-free grammars. I've found one paper, which seems to simplify the problem too much (in addition to some technical mistakes, as far as I can tell). ...
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### What effect would using different types of orders have on a binary search tree?

Recently, I was coding a comparator function for use in a set backed by a binary search tree, and the set kept saying that it didn't contain elements that I had previously added to it. I eventually ...
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### Number of subsets on a set with partial order

Given a set $S$ with strict partial order $<$. Let $A\subseteq S$ be a downward-closed subset of $S$ (in other words, if $a<b$ and $b\in A$, then $a\in A$). How many subsets of $S$ are downward-...
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### On finding a chain decomposition of a Partial Order

I am reading a paper by Daskalakis et al. entitled "Sorting and Selection in Posets". http://arxiv.org/abs/0707.1532 In that paper it is presented an enhancement to the algorithm Poset-...
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### My exact divide-conquer algorithm for counting antichain in a poset?

This post is a little lengthy, thank your for your patience for reading. ^_^ As known, counting antichains in a poset is #P-complete, so it is NP-hard to get the exact answer. Following is my simple ...
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### Is counting maximal cliques in an incomparability graph #P-complete?

This question is motivated by a MathOverflow question by Peng Zhang. Valiant showed that counting maximal cliques in a general graph is #P-complete, but what if we restrict to incomparability graphs (...
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### reference for lexicographic path ordering

Can you recommend a good reference for reading about lexicographic/recursive path orderings? I'm currently reading about lpo's in Chapter 2 of the Handbook of Automated Reasoning, 'Resolution Theorem ...
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### Well Defined Ordering Relations in Object Oriented Type Systems [closed]

In any Object-Oriented type system the type relation of two objects A and B can be characterized in exactly one of the following ways: A has the same type as B A is a subtype of B B is a subtype of A ...