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informatik

MPI-I-98-1-009

Fully dynamic shortest paths and negative cycle detection on diagraphs with Arbitrary Arc Weights

Frigioni, D. and Marchetti-Spaccamela, A. and Nanni, U.

MPI-I-98-1-009. April 1998, 18 pages. | Status: available - back from printing | Next --> Entry | Previous <-- Entry

Abstract in LaTeX format:
We study the problem of maintaining the distances and the shortest
paths from a source node in a directed graph with arbitrary arc
weights, when weight updates of arcs are performed. We propose
algorithms that work for any digraph and have optimal space
requirements and query time. If a negative--length cycle is introduced
during weight decrease operations it is detected by the algorithms. The
proposed algorithms explicitly deal with zero--length cycles. The cost
of update operations depends on the class of the considered digraph
and on the number of the output updates. We show that, if the digraph
has a $k$-bounded accounting function (as in the case of digraphs with
genus, arboricity, degree, treewidth or pagenumber bounded by $k$) the
update procedures require $O(k\cdot n\cdot \log n)$ worst case
time. In the case of digraphs with $n$ nodes and $m$ arcs
$k=O(\sqrt{m})$, and hence we obtain $O(\sqrt{m}\cdot n \cdot \log n)$
worst case time per operation, which is better for a factor of
$O(\sqrt{m} / \log n)$ than recomputing everything from scratch after
each input update.

If we perform also insertions and deletions of arcs all the above
bounds become amortized.

Acknowledgement:
References to related material:

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BibTeX
@TECHREPORT{FrigioniMarchetti-SpaccamelaNanni98,
AUTHOR = {Frigioni, D. and Marchetti-Spaccamela, A. and Nanni, U.},
TITLE = {Fully dynamic shortest paths and negative cycle detection on diagraphs with Arbitrary Arc Weights},
TYPE = {Research Report},
INSTITUTION = {Max-Planck-Institut f{\"u}r Informatik},