[petsc-dev] TS Terminology

[Barry Smith]

> On Oct 20, 2017, at 11:35 AM, Emil Constantinescu <emconsta at mcs.anl.gov> wrote:
> 
> To me IFunction really means IFunction obtained from implicit part  (- potentially explicit part depending on the solver). It is not just the implicit part, it is the implicit function (not part). The default is just the part thing. To me this makes it simple, less interfaces and it is transparent to the user. This will change the interfaces in all solvers, will fix little and make up really long names along the way. I mean this may confuse users by implying that there are multiple parts whereas most users have just one.
> 
> My point is the following: how does this affect how Matt implements things? If you two find this is really worth it, I have nothing against it. To me it's just a name.

   The name absolutely has to be changed. But to what? And the manual page is WRONG! You cannot justify that no matter how much you want to keep the current confusing/inaccurate name.

   Barry


> 
> Emil
> 
> 
> On 10/20/17 11:22 AM, Barry Smith wrote:
>>   Emil, see my email just sent. We need to rename this function (and its Jacobian partner).
>>> On Oct 20, 2017, at 11:20 AM, Emil Constantinescu <emconsta at mcs.anl.gov> wrote:
>>> 
>>> 
>>> 
>>> Matt, that depends, if TS method is imex, then it computes just F, not F-G so your argument is not correct. If the method can do only implicit it computes F and subtracts G *if defined*. If the TS method can only do explicit and you define F then it fails.
>>> 
>>> Again, this has to do with the TS methods and PETSc doing the work for you of packing the functions in different ways.
>>> 
>>> Emil
>>> 
>>>>   Matt
>>>>    Now internally, because different solvers have different needs the
>>>>    IFunction ... presented to the TS solver may look differently. This
>>>>    is a design choice - if you are not a TS developer it should not
>>>>    affect you.
>>>>    This is a design decision: if implemented at this level, we avoid
>>>>    having every TS method be aware of the upper level functions.
>>>>    Emil
>>>> -- 
>>>> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
>>>> -- Norbert Wiener
>>>> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>