petsc-3.12.4 2020-02-04
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# DMStagPopulateLocalToGlobalInjective

populate an internal 1-to-1 local-to-global map

### Synopsis

    PetscErrorCode DMStagPopulateLocalToGlobalInjective(DM dm)

Collective

Creates an internal object which explicitly maps a single local degree of freedom to each global degree of freedom. This is used, if populated, instead of SCATTER_REVERSE_LOCAL with the (1-to-many, in general) global-to-local map, when DMLocalToGlobal() is called with INSERT_VALUES. This allows usage, for example, even in the periodic, 1-rank case, where the inverse of the global-to-local map, even when restricted to on-rank communication, is non-injective. This is at the cost of storing an additional VecScatter object inside each DMStag object.

### Input Parameter

dm -the DMStag object

### Notes

In normal usage, library users shouldn't be concerned with this function, as it is called during DMSetUp(), when required.

Returns immediately if the internal map is already populated.

### Developer Notes

This could, if desired, be moved up to a general DM routine. It would allow, for example, DMDA to support DMLocalToGlobal() with INSERT_VALUES, even in the single-rank periodic case.

### See Also

DMSTAG, DMLocalToGlobal(), VecScatter

### Level

developer

### Location

src/dm/impls/stag/stagutils.c

### Implementations

DMStagPopulateLocalToGlobalInjective_1d in src/dm/impls/stag/stag1d.c
DMStagPopulateLocalToGlobalInjective_2d in src/dm/impls/stag/stag2d.c
DMStagPopulateLocalToGlobalInjective_3d in src/dm/impls/stag/stag3d.c
Index of all DMSTAG routines
Table of Contents for all manual pages
Index of all manual pages