#include "petscsnes.h" #include "petscdmshell.h" #include "petscsys.h" PetscErrorCode SNESSetJacobian(SNES snes,Mat A,Mat B,PetscErrorCode (*func)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void *ctx)Logically Collective on SNES and Mat
| snes | - the SNES context | |
| A | - Jacobian matrix | |
| B | - preconditioner matrix (usually same as the Jacobian) | |
| func | - Jacobian evaluation routine (if PETSC_NULL then SNES retains any previously set value) | |
| ctx | - [optional] user-defined context for private data for the Jacobian evaluation routine (may be PETSC_NULL) (if PETSC_NULL then SNES retains any previously set value) |
func (SNES snes,Vec x,Mat *A,Mat *B,int *flag,void *ctx);
| x | - input vector | |
| A | - Jacobian matrix | |
| B | - preconditioner matrix, usually the same as A | |
| flag | - flag indicating information about the preconditioner matrix structure (same as flag in KSPSetOperators()), one of SAME_NONZERO_PATTERN,DIFFERENT_NONZERO_PATTERN,SAME_PRECONDITIONER | |
| ctx | - [optional] user-defined Jacobian context |
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 A matrix and B matrix are different you must call MatAssemblyBegin/End() on each matrix.
If using SNESDefaultComputeJacobianColor() 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.
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