petsc-3.13.6 2020-09-29

SNESLineSearchShellSetUserFunc

Sets the user function for the SNESLineSearch Shell implementation.

PetscErrorCode SNESLineSearchShellSetUserFunc(SNESLineSearch linesearch, SNESLineSearchUserFunc func, void *ctx)

Not Collective

	linesearch	- SNESLineSearch context
	func	- function implementing the linesearch shell.
	ctx	- context for func

	linesearch	- the linesearch instance
	ctx	- the above mentioned context

 PetscErrorCode shellfunc(SNESLineSearch linesearch,void * ctx)

    Vec  X,Y,F,W,G;

    SNES snes;

    PetscFunctionBegin;

    ierr = SNESLineSearchGetSNES(linesearch,&snes);CHKERRQ(ierr);

    ierr = SNESLineSearchSetReason(linesearch,SNES_LINESEARCH_SUCCEEDED);CHKERRQ(ierr);

    ierr = SNESLineSearchGetVecs(linesearch,&X,&F,&Y,&W,&G);CHKERRQ(ierr);

    .. determine lambda using W and G as work vecs..

    ierr = VecAXPY(X,-lambda,Y);CHKERRQ(ierr);

    ierr = SNESComputeFunction(snes,X,F);CHKERRQ(ierr);

    ierr = SNESLineSearchComputeNorms(linesearch);CHKERRQ(ierr);

    PetscFunctionReturn(0);

...

 ierr = SNESGetLineSearch(snes, &linesearch);CHKERRQ(ierr);

 ierr = SNESLineSearchSetType(linesearch, SNESLINESEARCHSHELL);CHKERRQ(ierr);

 ierr = SNESLineSearchShellSetUserFunc(linesearch, shellfunc, NULL);CHKERRQ(ierr);

advanced