[petsc-users] Question about NASM initialization

[Matthew Knepley]

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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