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# DMPlexMetricGetHausdorffNumber
Get the metric Hausdorff number 
## Synopsis
```
#include "petscdmplex.h"   
PetscErrorCode DMPlexMetricGetHausdorffNumber(DM dm, PetscReal *hausd)
```

## Input parameters

- ***dm    -*** The `DM`



## Output parameters

- ***hausd -*** The metric Hausdorff number





## Notes
The Hausdorff number imposes the maximal distance between the piecewise linear approximation of the
boundary and the reconstructed ideal boundary. Thus, a low Hausdorff parameter leads to refine the
high curvature areas. By default, the Hausdorff value is set to 0.01, which is a suitable value for
an object of size 1 in each direction. For smaller (resp. larger) objects, you may need to decrease
(resp. increase) the Hausdorff parameter. (Taken from
https://www.mmgtools.org/mmg-remesher-try-mmg/mmg-remesher-options/mmg-remesher-option-hausd).

This is only used by Mmg and ParMmg (not Pragmatic).


## See Also
 `DMPLEX`, `DMPlexMetricGetGradationFactor()`, `DMPlexMetricSetHausdorffNumber()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/plexmetric.c.html#DMPlexMetricGetHausdorffNumber">src/dm/impls/plex/plexmetric.c</A>


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


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