DMPlexSectionLoad#

Loads section into a DMPLEX

Synopsis#

#include "petscdmplex.h"   
PetscErrorCode DMPlexSectionLoad(DM dm, PetscViewer viewer, DM sectiondm, PetscSF globalToLocalPointSF, PetscSF *globalDofSF, PetscSF *localDofSF)

Collective

Input Parameters#

dm - The DM that represents the topology
viewer - The PetscViewer that represents the on-disk section (sectionA)
sectiondm - The DM into which the on-disk section (sectionA) is migrated
globalToLocalPointSF - The PetscSF returned by DMPlexTopologyLoad() when loading dm from viewer

Output Parameters

globalDofSF - The PetscSF that migrates any on-disk Vec data associated with sectionA into a global Vec associated with the sectiondm’s global section (NULL if not needed)
localDofSF - The PetscSF that migrates any on-disk Vec data associated with sectionA into a local Vec associated with the sectiondm’s local section (NULL if not needed)

Notes#

This function is a wrapper around PetscSectionLoad(); it loads, in addition to the raw section, a list of global point numbers that associates each on-disk section point with a global point number in [0, NX), where NX is the number of topology points in dm. Noting that globalToLocalPointSF associates each topology point in dm with a global number in [0, NX), one can readily establish an association of the on-disk section points with the topology points.

In general dm and sectiondm are two different objects, the former carrying the topology and the latter carrying the section, and have been given a topology name and a section name, respectively, with PetscObjectSetName(). In practice, however, they can be the same object if it carries both topology and section; in that case the name of the object is used as both the topology name and the section name.

The output parameter, globalDofSF (localDofSF), can later be used with DMPlexGlobalVectorLoad() (DMPlexLocalVectorLoad()) to load on-disk vectors into global (local) vectors associated with sectiondm’s global (local) section.

Example using 2 processes#

  NX (number of points on dm): 4
  sectionA                   : the on-disk section
  vecA                       : a vector associated with sectionA
  sectionB                   : sectiondm's local section constructed in this function
  vecB (local)               : a vector associated with sectiondm's local section
  vecB (global)              : a vector associated with sectiondm's global section

                                     rank 0    rank 1
  vecA (global)                  : [.0 .4 .1 | .2 .3]        <- to be loaded in DMPlexGlobalVectorLoad() or DMPlexLocalVectorLoad()
  sectionA->atlasOff             :       0 2 | 1             <- loaded in PetscSectionLoad()
  sectionA->atlasDof             :       1 3 | 1             <- loaded in PetscSectionLoad()
  sectionA's global point numbers:       0 2 | 3             <- loaded in DMPlexSectionLoad()
  [0, NX)                        :       0 1 | 2 3           <- conceptual partition used in globalToLocalPointSF
  sectionB's global point numbers:     0 1 3 | 3 2           <- associated with [0, NX) by globalToLocalPointSF
  sectionB->atlasDof             :     1 0 1 | 1 3
  sectionB->atlasOff (no perm)   :     0 1 1 | 0 1
  vecB (local)                   :   [.0 .4] | [.4 .1 .2 .3] <- to be constructed by calling DMPlexLocalVectorLoad() with localDofSF
  vecB (global)                  :    [.0 .4 | .1 .2 .3]     <- to be constructed by calling DMPlexGlobalVectorLoad() with globalDofSF

where “|” represents a partition of loaded data, and global point 3 is assumed to be owned by rank 0.