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# DMProjectField

This projects a given function of the input fields into the function space provided by a `DM`, putting the coefficients in a global vector.

## Synopsis

    #include "petscdm.h"
    #include "petscdmda.h"
    #include "petscdmplex.h"
    #include "petscdmswarm.h"
    #include "petscksp.h"
    PetscErrorCode DMProjectField(DM dm, PetscReal time, Vec U, void (**funcs)(PetscInt dim, PetscInt Nf, PetscInt NfAux, const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[], const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[], PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f[]), InsertMode mode, Vec X)

Collective

## Input Parameters

- dm - The `DM`

- time - The time

- U - The input field vector

- funcs - The functions to evaluate, one per field

- mode - The insertion mode for values

## Output Parameter

- X - The output vector

## Calling sequence of `funcs`

- dim - The spatial dimension

- Nf - The number of input fields

- NfAux - The number of input auxiliary fields

- uOff - The offset of each field in `u`

- uOff_x - The offset of each field in `u_x`

- u - The field values at this point in space

- u_t - The field time derivative at this point in space (or `NULL`)

- u_x - The field derivatives at this point in space

- aOff - The offset of each auxiliary field in `u`

- aOff_x - The offset of each auxiliary field in `u_x`

- a - The auxiliary field values at this point in space

- a_t - The auxiliary field time derivative at this point in space (or `NULL`)

- a_x - The auxiliary field derivatives at this point in space

- t - The current time

- x - The coordinates of this point

- numConstants - The number of constants

- constants - The value of each constant

- f - The value of the function at this point in space

## Note

There are three different `DM`s that potentially interact in this function. The output `dm`, specifies the layout of the values calculates by the function. The input `DM`, attached to `U`, may be different. For example, you can input the solution over the full domain, but output over a piece of the boundary, or a subdomain. You can also output a different number of fields than the input, with different discretizations. Last the auxiliary `DM`, attached to the auxiliary field vector, which is attached to `dm`, can also be different. It can have a different topology, number of fields, and discretizations.

## See Also

DM Basics, `DM`, `DMProjectFieldLocal()`, `DMProjectFieldLabelLocal()`, `DMProjectFunction()`, `DMComputeL2Diff()`

## Level

advanced

## Location

src/ksp/ksp/utils/dm/dmproject.c

## Examples

src/ts/tutorials/ex76.c
src/snes/tutorials/ex13.c
src/ts/tutorials/ex30.c
src/snes/tutorials/ex12.c

Index of all DM routines
Table of Contents for all manual pages
Index of all manual pages