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# PetscViewerHDF5GetCollective
Return flag whether collective MPI-IO transfer mode is used for HDF5 reads and writes. 
## Synopsis
```
#include "petscviewerhdf5.h" 
PetscErrorCode PetscViewerHDF5GetCollective(PetscViewer viewer, PetscBool *flg)
```
Not Collective


## Input Parameter

- ***viewer -*** the `PETSCVIEWERHDF5` `PetscViewer`



## Output Parameter

- ***flg -*** the flag





## Note
This setting works correctly only since HDF5 1.10.3 and if HDF5 was installed for MPI. For older versions, `PETSC_FALSE` will be always returned.
For more details, see `PetscViewerHDF5SetCollective()`.


## See Also
 [](sec_viewers), `PETSCVIEWERHDF5`, `PetscViewerHDF5SetCollective()`, `PetscViewerCreate()`, `PetscViewerSetType()`, `PetscViewerHDF5Open()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/hdf5/hdf5v.c.html#PetscViewerHDF5GetCollective">src/sys/classes/viewer/impls/hdf5/hdf5v.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/hdf5/hdf5v.c.html#PetscViewerHDF5GetCollective_HDF5">PetscViewerHDF5GetCollective_HDF5 in src/sys/classes/viewer/impls/hdf5/hdf5v.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/classes/viewer/impls/hdf5/hdf5v.c)


[Index of all Viewer routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)