Abstract
The problem of partitioning an orthogonal polyhedron P into a minimum number of 3D rectangles is known to be NP-hard. In this paper, we first develop a 4-approximation algorithm for the special case of the problem in which P is a 3D histogram. It runs in \(O(m \log m)\) time, where m is the number of corners in P. We then apply it to exactly compute the arithmetic matrix product of two \(n \times n\) matrices A and B with nonnegative integer entries, yielding a method for computing \(A \times B\) in \(\tilde{O}(n^2 + \min \{ r_A r_B,\, n \min \{r_A,\ r_B\}\})\) time, where \(\tilde{O}\) suppresses polylogarithmic (in n) factors and where \(r_A\) and \(r_B\) denote the minimum number of 3D rectangles into which the 3D histograms induced by A and B can be partitioned, respectively.
Published Version
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