petsc-master 2019-05-24
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Returns the flags for determining variable influence

### Synopsis

#include "petscdm.h"
#include "petscdmlabel.h"
#include "petscds.h"
PetscErrorCode DMGetAdjacency(DM dm, PetscInt f, PetscBool *useCone, PetscBool *useClosure)

Not collective

### Input Parameters

 dm - The DM object f - The field number, or PETSC_DEFAULT for the default adjacency

### Output Parameter

 useCone - Flag for variable influence starting with the cone operation useClosure - Flag for variable influence using transitive closure

### Notes

    FEM:   Two points p and q are adjacent if q \in closure(star(p)),   useCone = PETSC_FALSE, useClosure = PETSC_TRUE

    FVM:   Two points p and q are adjacent if q \in support(p+cone(p)), useCone = PETSC_TRUE,  useClosure = PETSC_FALSE

    FVM++: Two points p and q are adjacent if q \in star(closure(p)),   useCone = PETSC_TRUE,  useClosure = PETSC_TRUE

Further explanation can be found in the User's Manual Section on the Influence of Variables on One Another.