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# 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/ex1f.F90
src/vec/is/sf/tutorials/ex1.c

## Implementations

PetscSFGetRootRanks_Allgatherv() in src/vec/is/sf/impls/basic/allgatherv/sfallgatherv.c

Index of all PetscSF routines
Table of Contents for all manual pages
Index of all manual pages