#include "petscdmplex.h" PetscErrorCode DMPlexGetTree(DM dm, PetscSection *parentSection, PetscInt *parents[], PetscInt *childIDs[], PetscSection *childSection, PetscInt *children[])
| parentSection | - a section describing the tree: a point has a parent if it has 1 dof in the section; the section offset indexes the parent and childID list | |
| parents | - a list of the point parents | |
| childIDs | - identifies the relationship of the child point to the parent point; if there is a reference tree, then the child corresponds to the point in the reference tree with index childID | |
| childSection | - the inverse of the parent section | |
| children | - a list of the point children |