PETSc version 3.17.5

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 on DM

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 SF returned by DMPlexTopologyLoad() when loading dm from viewer

Output Parameters

	globalDofSF	- The SF 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 SF 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.

Level

advanced

Location

src/dm/impls/plex/plex.c
Index of all DMPLEX routines
Table of Contents for all manual pages
Index of all manual pages