:orphan:
# 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
[](ch_stag), `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
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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/dm/impls/stag/stagutils.c)
[Index of all DMStag routines](index.md)
[Table of Contents for all manual pages](/manualpages/index.md)
[Index of all manual pages](/manualpages/singleindex.md)