petsc-3.4.2 2013-07-02

# SNESSetJacobian

Sets the function to compute Jacobian as well as the location to store the matrix.

### Synopsis

    #include "petscsnes.h"
    PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*SNESJacobianFunction)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void *ctx)

Logically Collective on SNES and Mat

### Input Parameters

| snes | - the SNES context
| Amat | - the matrix that defines the (approximate) Jacobian
| Pmat | - the matrix to be used in constructing the preconditioner, usually the same as Amat.
| SNESJacobianFunction | - Jacobian evaluation routine (if NULL then SNES retains any previously set value)
| ctx | - [optional] user-defined context for private data for the Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)

### Notes

See KSPSetOperators() for important information about setting the flag output parameter in the routine func(). Be sure to read this information!

The routine func() takes Mat * as the matrix arguments rather than Mat. This allows the Jacobian evaluation routine to replace A and/or B with a completely new new matrix structure (not just different matrix elements) when appropriate, for instance, if the nonzero structure is changing throughout the global iterations.

If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on each matrix.

If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument must be a MatFDColoring.

Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian. One common example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.

### Keywords

SNES, nonlinear, set, Jacobian, matrix

### See Also

KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, SNESJacobianFunction, SNESSetPicard()

Level:beginner
Location:src/snes/interface/snes.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages

### Examples

src/snes/examples/tutorials/ex1.c.html
src/snes/examples/tutorials/ex2.c.html
src/snes/examples/tutorials/ex3.c.html
src/snes/examples/tutorials/ex5s.c.html
src/snes/examples/tutorials/ex10.c.html
src/snes/examples/tutorials/ex12.c.html
src/snes/examples/tutorials/ex14.c.html
src/snes/examples/tutorials/ex15.c.html
src/snes/examples/tutorials/ex18.c.html
src/snes/examples/tutorials/ex20.c.html
src/snes/examples/tutorials/ex22.c.html