SNESSetFunction

Sets the function evaluation routine and function vector for use by the SNES routines in solving systems of nonlinear equations.

#include "petscsnes.h"  
int SNESSetFunction(SNES snes,Vec r,int (*func)(SNES,Vec,Vec,void*),void *ctx)

Collective on SNES

	snes	- the SNES context
	func	- function evaluation routine
	r	- vector to store function value
	ctx	- [optional] user-defined context for private data for the function evaluation routine (may be PETSC_NULL)

   func (SNES snes,Vec x,Vec f,void *ctx);

f -function vector

ctx -optional user-defined function context

The Newton-like methods typically solve linear systems of the form

     f'(x) x = -f(x),

where f'(x) denotes the Jacobian matrix and f(x) is the function.

SNES, nonlinear, set, function