[petsc-users] question

[Kong, Fande]

If you are using the matrix-free method, the number of  function
evaluations is way more  than the number of Newton iterations.

Fande,

On Mon, Oct 24, 2016 at 2:01 PM, Justin Chang <jychang48 at gmail.com> wrote:

> Sorry forgot to hit reply all
>
> On Monday, October 24, 2016, Justin Chang <jychang48 at gmail.com> wrote:
>
>> It depends on your SNES solver. A SNES iteration could involve more than
>> one function evaluation (e.g., line searching). Also, -snes_monitor may say
>> 3 iterations whereas -snes_view might indicate 4 function evaluations which
>> could suggest that the first call was for computing the initial residual.
>>
>> On Mon, Oct 24, 2016 at 2:22 PM, Gideon Simpson <gideon.simpson at gmail.com
>> > wrote:
>>
>>> I notice that if I use -snes_view,
>>>
>>> I see lines like:
>>>   total number of linear solver iterations=20
>>>   total number of function evaluations=5
>>> Just to clarify, the number of "function evaluations" corresponds to the
>>> number of Newton (or Newton like) steps, and the total "number of linear
>>> solver iterations” is the total number of iterations needed to solve the
>>> linear problem at each Newton iteration.  Is that correct?  So in the
>>> above, there are 5 steps of Newton and a total of 20 iterations of the
>>> linear solver across all 5 Newton steps.
>>>
>>> -gideon
>>>
>>>
>>
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