:orphan:
# DMLabelCompare
Compare two `DMLabel` objects 
## Synopsis
```
#include "petscdmlabel.h"   
#include "petscsection.h"   
PetscErrorCode DMLabelCompare(MPI_Comm comm, DMLabel l0, DMLabel l1, PetscBool *equal, char **message)
```
Collective; No Fortran Support


## Input Parameters

- ***comm -*** Comm over which to compare labels
- ***l0 -*** First `DMLabel`
- ***l1 -*** Second `DMLabel`


Output Parameters

- ***equal   -*** (Optional) Flag whether the two labels are equal
- ***message -*** (Optional) Message describing the difference





## Notes
The output flag equal is the same on all processes.
If it is passed as `NULL` and difference is found, an error is thrown on all processes.
Make sure to pass `NULL` on all processes.

The output message is set independently on each rank.
It is set to `NULL` if no difference was found on the current rank. It must be freed by user.
If message is passed as `NULL` and difference is found, the difference description is printed to stderr in synchronized manner.
Make sure to pass `NULL` on all processes.

For the comparison, we ignore the order of stratum values, and strata with no points.

The communicator needs to be specified because currently `DMLabel` can live on `PETSC_COMM_SELF` even if the underlying `DM` is parallel.


## See Also
 `DMLabel`, `DM`, `DMCompareLabels()`, `DMLabelGetNumValues()`, `DMLabelGetDefaultValue()`, `DMLabelGetNonEmptyStratumValuesIS()`, `DMLabelGetStratumIS()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/label/dmlabel.c.html#DMLabelCompare">src/dm/label/dmlabel.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/label/tutorials/ex1.c.html">src/dm/label/tutorials/ex1.c</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/dm/label/dmlabel.c)


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