[petsc-users] Question about NASM initialization

[Takahashi, Tadanaga]

Ok, thanks for the clarification.

On Thu, Apr 6, 2023 at 10:25 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Apr 6, 2023 at 10:21 AM Takahashi, Tadanaga <tt73 at njit.edu> wrote:
>
>> I am following up from the last inquiry. I read the source code nasm.c
>> <https://petsc.org/release/src/snes/impls/nasm/nasm.c.html> and it looks
>> like sub-snes iteration is being initialized with a scatter call from the
>> previous solution. In other words, if I use Newton's method for the local
>> solver, then in each NASM iteration the Newton's method uses the previous
>> local solution as the initial guess. Can anyone confirm this?
>>
>
> This is the intention. There are not many tests, so it is possible there
> is a bug, but it is supposed to use the existing solution.
>
>   Thanks,
>
>     Matt
>
>
>> On Sun, Apr 2, 2023 at 6:14 PM Takahashi, Tadanaga <tt73 at njit.edu> wrote:
>>
>>> Hello PETSc devs,
>>>
>>> I am using SNES NASM with Newton LS on the sub-SNES. I was wondering how
>>> the sub-SNES chooses the initial guess during each NASM iteration. Is it
>>> using the previously computed solution or is it restarting from zero?
>>>
>>
>
> --
> 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.cse.buffalo.edu/~knepley/>
>
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