:orphan:
# PetscSFGetRootRanks
Get root ranks and number of vertices referenced by leaves on this process
## Synopsis
```
#include "petscsf.h"
PetscErrorCode PetscSFGetRootRanks(PetscSF sf, PetscInt *nranks, const PetscMPIInt **ranks, const PetscInt **roffset, const PetscInt **rmine, const PetscInt **rremote)
```
Not Collective
## Input Parameter
- ***sf -*** star forest
## Output Parameters
- ***nranks -*** number of ranks referenced by local part
- ***ranks -*** [`nranks`] array of ranks
- ***roffset -*** [`nranks`+1] offset in `rmine`/`rremote` for each rank
- ***rmine -*** [`roffset`[`nranks`]] concatenated array holding local indices referencing each remote rank
- ***rremote -*** [`roffset`[`nranks`]] concatenated array holding remote indices referenced for each remote rank
## See Also
`PetscSF`, `PetscSFGetLeafRanks()`
## Level
developer
## Location
src/vec/is/sf/interface/sf.c
## Examples
src/vec/is/sf/tutorials/ex1.c
src/vec/is/sf/tutorials/ex1f.F90
## Implementations
PetscSFGetRootRanks_Allgatherv in src/vec/is/sf/impls/basic/allgatherv/sfallgatherv.c
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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/vec/is/sf/interface/sf.c)
[Index of all PetscSF routines](index.md)
[Table of Contents for all manual pages](/manualpages/index.md)
[Index of all manual pages](/manualpages/singleindex.md)