MPI-INF/SWS Research Reports 1991-2021

# MPI-I-2005-1-001

## Rank-maximal through maximum weight matchings

### Michail, Dimitrios

#### February 2005, 22 pages.

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##### Status: available - back from printing

Given a bipartite graph $G( V, E)$, $V = A \disjointcup B$ where $|V|=n, |E|=m$ and a partition of the edge set into $r \le m$ disjoint subsets $E = E_1 \disjointcup E_2 \disjointcup \dots \disjointcup E_r$, which are called ranks, the {\em rank-maximal matching} problem is to find a matching $M$ of $G$ such that $|M \cap E_1|$ is maximized and given that $|M \cap E_2|$, and so on. Such a problem arises as an optimization criteria over a possible assignment of a set of applicants to a set of posts. The matching represents the assignment and the ranks on the edges correspond to a ranking on the posts submitted by the applicants. The rank-maximal matching problem has been previously studied where a $O( r \sqrt n m )$ time and linear space algorithm~\cite{IKMMP} was presented. In this paper we present a new simpler algorithm which matches the running time and space complexity of the above algorithm. The new algorithm is based on a different approach, by exploiting that the rank-maximal matching problem can be reduced to a maximum weight matching problem where the weight of an edge of rank $i$ is $2^{ \ceil{\log n} (r-i)}$. By exploiting that these edge weights are steeply distributed we design a scaling algorithm which scales by a factor of $n$ in each phase. We also show that in each phase one maximum cardinality computation is sufficient to get a new optimal solution. This algorithm answers an open question raised on the same paper on whether the reduction to the maximum-weight matching problem can help us derive an efficient algorithm.

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URL to this document: https://domino.mpi-inf.mpg.de/internet/reports.nsf/NumberView/2005-1-001
BibTeX
@TECHREPORT{Michail2005,
AUTHOR = {Michail, Dimitrios},
TITLE = {Rank-maximal through maximum weight matchings},
TYPE = {Research Report},
INSTITUTION = {Max-Planck-Institut f{\"u}r Informatik},
ADDRESS = {Stuhlsatzenhausweg 85, 66123 Saarbr{\"u}cken, Germany},
NUMBER = {MPI-I-2005-1-001},
MONTH = {February},
YEAR = {2005},
ISSN = {0946-011X},
}