petsc-3.13.6 2020-09-29

MatMFFDComputeJacobian

Tells the matrix-free Jacobian object the new location at which Jacobian matrix vector products will be computed at, i.e. J(x) * a. The x is obtained from the SNES object (using SNESGetSolution()).

Synopsis

#include "petscsnes.h" 
#include "petscdm.h"   
PetscErrorCode  MatMFFDComputeJacobian(SNES snes,Vec x,Mat jac,Mat B,void *dummy)

Logically Collective on SNES

Input Parameters

	snes	- the nonlinear solver context
	x	- the point at which the Jacobian vector products will be performed
	jac	- the matrix-free Jacobian object
	B	- either the same as jac or another matrix type (ignored)
	flag	- not relevent for matrix-free form
	dummy	- the user context (ignored)

Warning

If MatMFFDSetBase() is ever called on jac then this routine will NO longer get the x from the SNES object and MatMFFDSetBase() must from that point on be used to change the base vector x.

Notes

This can be passed into SNESSetJacobian() as the Jacobian evaluation function argument when using a completely matrix-free solver, that is the B matrix is also the same matrix operator. This is used when you select -snes_mf but rarely used directly by users. (All this routine does is call MatAssemblyBegin/End() on the Mat jac.)

Level

developer

Location

src/snes/mf/snesmfj.c
Index of all SNES routines
Table of Contents for all manual pages
Index of all manual pages