Positive spanning sets span a given vector space by nonnegative linear combinations of their elements. These have attracted significant attention in recent years, owing to their extensive use in derivative-free optimization. In this setting, the quality of a positive spanning set is assessed through its cosine measure, a geometric quantity that expresses how well such a set covers the space of interest. In this paper, we investigate the construction of positive $k$-spanning sets with geometrical guarantees.Our results build on recently identified positive spanning sets, called orthogonally structured positive bases. We first describe how to identify such sets and compute their cosine measures efficiently. We then focus our study on positive $k$-spanning sets, for which we provide a complete description, as well as a new notion of cosine measure that accounts for the resilient nature of such sets. By combining our results, we are able to use orthogonally structured positive bases to create positive $k$-spanning sets with guarantees on the value of their cosine measures.

翻译：正张成集通过其元素的非负线性组合张成给定的向量空间。近年来，由于其在无导数优化中的广泛应用，这类集合引起了广泛关注。在此背景下，正张成集的质量通过余弦度来评估，这是一种表示集合覆盖目标空间程度的几何量。本文研究具有几何保证的正$k$-张成集的构造。我们的结果建立在最近发现的称为正交结构正基的正张成集之上。首先，我们描述了如何识别这类集合并高效计算其余弦度。随后，我们专注于正$k$-张成集的研究，为此提供了完整的描述，以及一种考虑此类集合弹性性质的新余弦度概念。通过综合我们的结果，我们能够利用正交结构正基构造出具有余弦度值保证的正$k$-张成集。