منابع مشابه
Integer equal flows
The integer equal flow problem is an NP-hard network flow problem, in which all arcs in given sets R1, . . . , R` must carry equal flow. We show that this problem is effectively inapproximable, even if the cardinality of each set Rk is two. When ` is fixed, it is solvable in polynomial time. © 2009 Elsevier B.V. All rights reserved.
متن کاملVector Flows and Integer Flows
A vector Sd-flow is a flow whose flow values are vectors in Sd, where Sd is the set of all unit vectors in Rd+1. Jain [Open Problem Garden, http://www.openproblemgarden.org/op/unit vector flows (2007)] and Thomassen [J. Combin. Theory Ser. B., 108 (2014), pp. 81–91] proved that a graph has a vector S1-flow if it has a nowhere-zero integer 3-flow. Thomassen [J. Combin. Theory Ser. B., 108 (2014)...
متن کاملInteger Multicommodity Flows with Reduced
Given a supply graph G = (V; E), a demand graph H = (T; D), edge capacities c : E 7 ! II N and requests r : D 7 ! II N, we consider the problem of nding integer multiiows subject to c; r. Korach and Penn constructed approximate integer multiiows for planar graphs, but no results were known for the general case. Via derandomization we present a polynomial-time approximation algorithm. There are ...
متن کاملInteger flows and cycle covers
Results related to integer flows and cycle covers are presented. A cycle cover of a graph G is a collection %Y of cycles of G which covers all edges of G; U is called a cycle m-cover of G if each edge of G is covered exactly m times by the members of V. By using Seymour’s nowhere-zero 6-flow theorem, we prove that every bridgeless graph has a cycle 6-cover associated to covering of the edges by...
متن کاملCounting Integer Flows in Networks
This paper discusses analytic algorithms and software for the enumeration of all integer flows inside a network. Concrete applications abound in graph theory, representation theory, and statistics. Our methods are based on the study of rational functions with poles on arrangements of hyperplanes; they surpass traditional exhaustive enumeration and can even yield formulas when the input data con...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Operations Research Letters
سال: 2009
ISSN: 0167-6377
DOI: 10.1016/j.orl.2009.03.006