Min-plus matrix multiplication

Template:No footnotes Min-plus matrix multiplication, also known as distance product, is an operation on matrices.

Given two $n\times n$ matrices $A=(a_{ij})$ and $B=(b_{ij})$, their distance product $C=(c_{ij})=A\star B$ is defined as an $n\times n$ matrix such that $c_{ij}={\min }_{k=1}^n\{a_{ik}+b_{kj}\}$. This is standard matrix multiplication for the semi-ring of tropical numbers in the min convention.

This operation is closely related to the shortest path problem. If $W$ is an $n\times n$ matrix containing the edge weights of a graph, then $W^k$ gives the distances between vertices using paths of length at most $k$ edges, and $W^n$ is the distance matrix of the graph.

References

• Uri Zwick. 2002. All pairs shortest paths using bridging sets and rectangular matrix multiplication. J. ACM 49, 3 (May 2002), 289–317.
• Liam Roditty and Asaf Shapira. 2008. All-Pairs Shortest Paths with a Sublinear Additive Error. ICALP '08, Part I, LNCS 5125, pp. 622–633, 2008.

See also

• Floyd–Warshall algorithm
• Tropical geometry

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