PETSc version 3.17.0
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# DMComputeL2FieldDiff

This function computes the L_2 difference between a function u and an FEM interpolant solution u_h, separated into field components.

### Synopsis

    #include "petscdm.h"
    #include "petscdmlabel.h"
    #include "petscds.h"
    PetscErrorCode DMComputeL2FieldDiff(DM dm, PetscReal time, PetscErrorCode (**funcs)(PetscInt, PetscReal, const PetscReal [], PetscInt, PetscScalar *, void *), void **ctxs, Vec X, PetscReal diff[])

Collective on dm

### 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.
| X | - The coefficient vector u_h, a global vector

### Output Parameter

| diff | - The array of differences, ||u^f - u^f_h||_2

### See Also

DMProjectFunction(), DMComputeL2FieldDiff(), DMComputeL2GradientDiff()

### Level

developer

### Location

src/dm/interface/dm.c

### Examples

src/ts/tutorials/ex46.c.html

### Implementations

DMComputeL2FieldDiff_pforest(DM dm, PetscReal time, PetscErrorCode (**funcs) in src/dm/impls/forest/p4est/pforest.h
DMComputeL2FieldDiff_Plex(DM dm, PetscReal time, PetscErrorCode (**funcs) in src/dm/impls/plex/plexfem.c
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