petsc-3.6.2 2015-10-02
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# PetscDSGetResidual

Get the pointwise residual function for a given test field

### Synopsis

    #include "petscds.h"
    PetscErrorCode PetscDSGetResidual(PetscDS prob, PetscInt f,
                                      void (**f0)(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[], PetscScalar f0[]),
                                      void (**f1)(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[], PetscScalar f1[]))

Not collective

### Input Parameters

| prob | - The PetscDS
| f | - The test field number

### Output Parameters

| f0 | - integrand for the test function term
| f1 | - integrand for the test function gradient term

### Note: We are using a first order FEM model for the weak form

\int_\Omega \phi f_0(u, u_t, \nabla u, x, t) + \nabla\phi \cdot {\vec f}_1(u, u_t, \nabla u, x, t)

### The calling sequence for the callbacks f0 and f1 is given by

    f0(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[], PetscScalar f0[])

| dim | - the spatial dimension
| Nf | - the number of fields
| uOff | - the offset into u[] and u_t[] for each field
| uOff_x | - the offset into u_x[] for each field
| u | - each field evaluated at the current point
| u_t | - the time derivative of each field evaluated at the current point
| u_x | - the gradient of each field evaluated at the current point
| aOff | - the offset into a[] and a_t[] for each auxiliary field
| aOff_x | - the offset into a_x[] for each auxiliary field
| a | - each auxiliary field evaluated at the current point
| a_t | - the time derivative of each auxiliary field evaluated at the current point
| a_x | - the gradient of auxiliary each field evaluated at the current point
| t | - current time
| x | - coordinates of the current point
| f0 | - output values at the current point

### See Also

PetscDSSetResidual()

Level:intermediate
Location: src/dm/dt/interface/dtds.c
Index of all DM routines
Table of Contents for all manual pages
Index of all manual pages