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# PetscFormKey
This key indicates how to use a set of pointwise functions defining part of a system of equations 
## Synopsis
```
typedef struct _PetscFormKey {
  DMLabel  label; /* The (label, value) select a subdomain */
  PetscInt value;
  PetscInt field; /* Selects the field for the test function */
  PetscInt part;  /* Selects the equation part. For example, LHS = 0 and RHS = 1 in IMEX methods. More pieces can be present for operator splitting methods. */
} PetscFormKey;
```
The subdomain on which to integrate is specified by (label, value), the test function field by (field), and the
piece of the equation by (part). For example, LHS = 0 and RHS = 1 in IMEX methods. More pieces can be present for
operator splitting methods.




## See Also
 `DMPlexSNESComputeResidualFEM()`, `DMPlexSNESComputeJacobianFEM()`, `DMPlexSNESComputeBoundaryFEM()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscdstypes.h.html#PetscFormKey">include/petscdstypes.h</A>


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