[petsc-dev] Tao Separable Objective deprecated

[Isaac, Tobin G]

That's for the explanation, Alp.

On January 4, 2019 4:45:34 PM EST, "Dener, Alp" <adener at anl.gov> wrote:
>Hi Isaac,
>
>On Jan 4, 2019, at 8:41 AM, Isaac, Tobin G via petsc-dev
><petsc-dev at mcs.anl.gov<mailto:petsc-dev at mcs.anl.gov>> wrote:
>
>
>I'm interested in exploring various method of multipliers approaches
>to optimization for separable objectives.  With the separable
>objective interface recently deprecated, how do you think I should go
>about doing this?
>
>The separable objective interface isn’t gone. We just changed
>terminology because “separable objective” was not an accurate
>description of what the function was doing. It was being used to define
>the residual for a nonlinear least-squares problem, so we’ve changed
>the function name to TaoSetResidualRoutine(). Otherwise the function
>signature is the same as before.
>
>In line with this change, we’ve also converted
>TaoSetSeparableObjectiveWeights() to TaoSetResidualWeights(). We’ve
>also added a TaoSetResidualJacobianRoutine() in order to support the
>regularized Gauss-Newton algorithm that has been added to TAO recently
>(Pounders never needed the least-squares Jacobian to be provided).
>
>If you were using Pounders before with the separable objective API, you
>can continue to do so still using the new function names. The
>functionality underneath hasn’t changed.
>
>
>In general, because on objective function is not an object, just a
>routine, how should we go about conveying structure in the objective?
>Do we prefer that data to be composed onto the Tao object?
>
>
>There is no support in TAO at the moment for actual separable objective
>functions. None of the algorithms in TAO have any understanding of
>structure in the objective, or try to do special things to take
>advantage of that structure. That is actually the main reason why we
>wanted to change the separable objective interface because it is
>misleading to the user, and suggests the existence of a TAO
>functionality that is not actually available.
>
>Thanks,
> Toby
>
>
>
>I hope this answers your questions!
>
>Best,
>——
>Alp Dener
>Argonne National Laboratory
>https://www.anl.gov/profile/alp-dener