:orphan:
# DMComputeL2DiffLocal
This function computes the L_2 difference between a function u and an FEM interpolant solution u_h. 
## Synopsis
```
#include "petscdmplex.h"   
PetscErrorCode DMPlexComputeL2DiffLocal(DM dm, PetscReal time, PetscErrorCode (**funcs)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar *, void *), void **ctxs, Vec localX, PetscReal *diff)
```
Collective


## Input Parameters

- ***dm     -*** The `DM`
- ***time   -*** The time
- ***funcs  -*** The functions to evaluate for each field component
- ***ctxs   -*** Optional array of contexts to pass to each function, or `NULL`.
- ***localX -*** The coefficient vector u_h, a local vector



## Output Parameter

- ***diff -*** The diff ||u - u_h||_2





## See Also
 [](ch_unstructured), `DM`, `DMPLEX`, `DMProjectFunction()`, `DMComputeL2FieldDiff()`, `DMComputeL2GradientDiff()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/plex/plexfem.c.html#DMComputeL2DiffLocal">src/dm/impls/plex/plexfem.c</A>


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