The alpha complex is a fundamental data structure from computational geometry, which encodes the topological type of a union of balls B(x;r)⊂Rm for x∈S, including a weighted version that allows for ...varying radii. It consists of the collection of “simplices” σ={x0,...,xk}⊂S, which correspond to nonempty (k+1)-fold intersections of cells in a radius-restricted version of the Voronoi diagram Vor(S,r). Existing algorithms for computing the alpha complex require that the points reside in low dimension because they begin by computing the entire Delaunay complex, which rapidly becomes intractable, even when the alpha complex is of a reasonable size. This paper presents a method for computing the alpha complex without computing the full Delaunay triangulation by applying Lagrangian duality, specifically an algorithm based on dual quadratic programming that seeks to rule simplices out rather than ruling them in.
We give robust recovery results for synchronization on the rotation group, Formula omitted. In particular, we consider an adversarial corruption setting, where a limited percentage of the ...observations are arbitrarily corrupted. We develop a novel algorithm that exploits Tukey depth in the tangent space of Formula omitted. This algorithm, called Depth Descent Synchronization, exactly recovers the underlying rotations up to an outlier percentage of Formula omitted, which corresponds to 1/4 for Formula omitted and 1/8 for Formula omitted. In the case of Formula omitted, we demonstrate that a variant of this algorithm converges linearly to the ground truth rotations. We implement this algorithm for the case of Formula omitted and demonstrate that it performs competitively on baseline synthetic data.
Predictive Algorithms for a Crisis Sotillo, Claudia L; Franco, Idalid; Arriaga, Alexander F
Critical care medicine,
07/2022, Volume:
50, Issue:
7
Journal Article
In this paper, we consider the problem of computing the rank of a block-structured symbolic matrix (a generic partitioned matrix) Formula omitted, where Formula omitted is a Formula omitted matrix ...over a field Formula omitted and Formula omitted is an indeterminate for Formula omitted and Formula omitted. This problem can be viewed as an algebraic generalization of the bipartite matching problem and was considered by Iwata and Murota (SIAM J Matrix Anal Appl 16(3):719-734, 1995). Recent interests in this problem lie in the connection with non-commutative Edmonds' problem by Ivanyos et al. (Comput Complex 27:561-593, 2018) and Garg et al. (Found. Comput. Math. 20:223-290, 2020), where a result by Iwata and Murota implicitly states that the rank and non-commutative rank (nc-rank) are the same for this class of symbolic matrices. The main result of this paper is a simple and combinatorial Formula omitted-time algorithm for computing the symbolic rank of a Formula omitted-type generic partitioned matrix of size Formula omitted. Our algorithm is inspired by the Wong sequence algorithm by Ivanyos et al. for the nc-rank of a general symbolic matrix, and requires no blow-up operation, no field extension, and no additional care for bounding the bit-size. Moreover it naturally provides a maximum rank completion of A for an arbitrary field Formula omitted.
We consider the restricted inverse optimal value problem on shortest path under weighted Formula omitted norm on trees (RIOVSPT Formula omitted). It aims at adjusting some edge weights to minimize ...the total cost under weighted Formula omitted norm on the premise that the length of the shortest root-leaf path of the tree is lower-bounded by a given value D, which is just the restriction on the length of a given root-leaf path Formula omitted. If we ignore the restriction on the path Formula omitted, then we obtain the minimum cost shortest path interdiction problem on trees (MCSPIT Formula omitted). We analyze some properties of the problem (RIOVSPT Formula omitted) and explore the relationship of the optimal solutions between (MCSPIT Formula omitted) and (RIOVSPT Formula omitted). We first take the optimal solution of the problem (MCSPIT Formula omitted) as an initial infeasible solution of problem (RIOVSPT Formula omitted). Then we consider a slack problem Formula omitted, where the length of the path Formula omitted is greater than D. We obtain its feasible solutions gradually approaching to an optimal solution of the problem (RIOVSPT Formula omitted) by solving a series of subproblems Formula omitted. It aims at determining the only weight-decreasing edge on the path Formula omitted with the minimum cost so that the length of the shortest root-leaf path is no less than D. The subproblem can be solved by searching for a minimum cost cut in O(n) time. The iterations continue until the length of the path Formula omitted equals D. Consequently, the time complexity of the algorithm is Formula omitted and we present some numerical experiments to show the efficiency of the algorithm. Additionally, we devise a linear time algorithm for the problem (RIOVSPT Formula omitted) under unit Formula omitted norm.
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