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Answering distance queries in directed graphs using fast matrix multiplication
Pittsburgh, Pennsylvania, USA October 23-October 25
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/SFCS.2005.2046th Annual IEEE Symposium on Foundat ...
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Raphael Yuster, University of Haifa
Uri Zwick, Tel Aviv University

Let G = (V, E,w) be a weighted directed graph, where w : \rm E \to {-M, . . . , 0, . . . , M}. We show that G can be preprocessed in O(m^\omega) time, where \omega < 2.376 is the exponent of fast matrix multiplication, such that subsequently, each distance \delta (\upsilon ,\nu ) in the graph, where \upsilon ,\nu \varepsilon V , can be computed exactly in O(n) time. We also present a tradeoff between the processing time and the query answering time. As a very special case, we obtain an O(m^\omega) time algorithm for the Single Source Shortest Paths (SSSP) problem for directed graphs with integer weights of absolute value at most M. For suf?ciently dense graphs, with small enough edge weights, this improves upon the O(m\sqrt n \log M) time algorithm of Goldberg. We note that even the case M = 1, in which all the edge weights are in {-1, 0, +1}, is an interesting case for which no improvement over Goldberg?s O(m\sqrt n ) algorithm was known. Our new Õ(n^\omega) algorithm is faster whenever m > n^{\omega - 1/2} \simeq n^{1.876}.

Citation:
Raphael Yuster, Uri Zwick, "Answering distance queries in directed graphs using fast matrix multiplication," focs, pp.389-396, 46th Annual IEEE Symposium on Foundations of Computer Science (FOCS'05), 2005
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