[petsc-users] Question about TaoLineSearchApply.

Jason Sarich jason.sarich at gmail.com
Sun May 25 09:10:36 CDT 2014

Hi Ce Qin,

Typically the MT line search accepts the first trial point, it is mostly
used to throw out a few terrible guesses and to help prevent stalling. You
should get a general idea of how much time is spent line searching just be
checking the number of TAO iterations versus the number of function
evaluations in -tao_view, and there are simple ways to access this
information directly if you need to.

There are some parameters for the line search that make it more or less
selective, but saving a few function evaluations here in the line search
will probably cost more evaluations in the broader view of the optimization
in general.

If you haven't done so yet, try the lmvm algorithm as a substitute for cg,
it works on the same information and usually performs a little better.


On Sun, May 25, 2014 at 8:12 AM, Ce Qin <qince168 at gmail.com> wrote:

>  Thanks, Jason. That's what I need.
> One more question, How many function and gradient evaluations one MT line
> search need?
> I'm doing geophysical inversion, function and gradient evaluation is very
> expensive, so I want to minimize the function calls. Do you have any
> suggestions?
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