# 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.

DMPlexSNESComputeResidualFEM(), DMPlexSNESComputeJacobianFEM(), DMPlexSNESComputeBoundaryFEM()