PETSc version 3.17.0
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# DMFieldEvaluateFV

Evaluate the mean of a field and its finite volume derivatives on a set of points.

### Synopsis

    #include "petscdmfield.h"
    #include "petscdmfield.h"
    PetscErrorCode DMFieldEvaluateFV(DMField field, IS cellIS, PetscDataType datatype, void *B, void *D, void *H)

Not collective

### Input Parameters

| field | - The DMField object
| cellIS | - Index set for cells on which to evaluate the field
| datatype | - The PetscDataType of the output arrays: either PETSC_REAL or PETSC_SCALAR. If the field is complex and datatype is PETSC_REAL, the real part of the field is returned.

### Output Parameters

| B | - pointer to data of size c * n * sizeof(datatype), where c is the number of components in the field. If B is not NULL, the values of the field are written in this array, varying first by component, then by point.
| D | - pointer to data of size d * c * n * sizeof(datatype). If D is not NULL, the values of the field's spatial derivatives are written in this array, varying first by the partial derivative component, then by field component, then by point.
| H | - pointer to data of size d * d * c * n * sizeof(datatype). If H is not NULL, the values of the field's second spatial derivatives are written in this array, varying first by the second partial derivative component, then by field component, then by point.

### See Also

DMFieldGetNumComponents(), DMFieldEvaluate(), DMFieldEvaluateFE()

### Level

intermediate

### Location

src/dm/field/interface/dmfield.c

### Examples

src/dm/field/tutorials/ex1.c.html

### Implementations

DMFieldEvaluateFV_DA in src/dm/field/impls/da/dmfieldda.c
DMFieldEvaluateFV_DS in src/dm/field/impls/ds/dmfieldds.c
Index of all DM routines
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