SPX meaning in Computing ?

In geometry, a simplex (plural: simplexes or simplices) is a generalization of the notion of a triangle or tetrahedron to arbitrary dimensions. The simplex is so-named because it represents the simplest possible polytope in any given space.

For example,

Specifically, a k-simplex is a k-dimensional polytope which is the convex hull of its k + 1 vertices. More formally, suppose the k + 1 points u 0 , … , u k ∈ R k {\displaystyle u_{0},\dots ,u_{k}\in \mathbb {R} ^{k}} are affinely independent, which means u 1 − u 0 , … , u k − u 0 {\displaystyle u_{1}-u_{0},\dots ,u_{k}-u_{0}} are linearly independent.Then, the simplex determined by them is the set of points