[petsc-users] Extending PETSC-SNES-VI to linear inequality constraints,

[subramanya sadasiva]

Thanks Jed. Being able to apply other pointwise constraints will be really helpful, even through implementation of a custom project function .Augmented lagrangian for the one extra constraint really ruins my convergence. Subramanya 
> From: jedbrown at mcs.anl.gov
> To: potaman at outlook.com; petsc-users at mcs.anl.gov
> CC: brune at mcs.anl.gov
> Subject: RE: [petsc-users] Extending PETSC-SNES-VI to linear inequality constraints,
> Date: Mon, 23 Dec 2013 21:54:42 -0700
> 
> subramanya sadasiva <potaman at outlook.com> writes:
> 
> > Hi Jed, I was just looking through the SNES documentation, I came
> > across SNESLineSearchSetVIFunctions. Is there an example of the use of
> > this function to implement and arbitrary projection?  Can I use this
> > to implement a function that projects the solution back into the
> > feasible region? I am assuming this should be able to handle simple
> > linear inequality constraints of the type that I have, which can be
> > applied pointwise.
> 
> Hmm, that interface is currently used by SNESVI *implementations* to
> communicate information to the SNESLineSearch object.  So while it may
> work to provide a custom projection, the current code will overwrite it,
> e.g., SNESSolve_VINEWTONRSLS in virs.c:
> 
>   ierr = SNESLineSearchSetVIFunctions(snes->linesearch, SNESVIProjectOntoBounds, SNESVIComputeInactiveSetFnorm);CHKERRQ(ierr);
> 
> Maybe Peter has further thoughts about adding other constraints to the
> SNESVI interface.  The restriction to simple bound constraints is a
> significant impediment, preventing its use for elastic contact and other
> applications.
 		 	   		  
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