Mesh resolution

[Ryan Yan]

Hi Rebecca,
Thanks for reminding me the half-spacing strategy, the 3*7 restriction
matrix in 1-D.

Yan

On Tue, Dec 15, 2009 at 10:37 PM, (Rebecca) Xuefei YUAN <xy2102 at columbia.edu
> wrote:

> Now PETSc treats the multigrid based on the half spacing strategy, thus
> they always do odd number of grids.
>
>
> R
>
> Quoting Ryan Yan <vyan2000 at gmail.com>:
>
>  Sorry, I forgot to cc to the group.
>>
>> BTW, if this is designed to have only odd number of points on the finer
>> level grid, can anyone provide a hint on the reasoning behind this?
>>
>> Thanks a lot,
>>
>> Yan
>>
>> On Tue, Dec 15, 2009 at 10:09 PM, Ryan Yan <vyan2000 at gmail.com> wrote:
>>
>>  Hi Rebecca,
>>> Thanks for the info. I noticed that rule; yet, it seems very difficult to
>>> bring up a finest grid with *even* number of pts.
>>>
>>> Yan
>>>
>>>
>>> On Tue, Dec 15, 2009 at 9:55 PM, (Rebecca) Xuefei YUAN <
>>> xy2102 at columbia.edu> wrote:
>>>
>>>  The relation between the coarser grid and finer grid is always half
>>>> spacing in either x-, y-, or z-direction.
>>>>
>>>> Thus, for your finest grid being 257x257x257, you need a coarser grid of
>>>> 129x129x129 on the coarse grid if your level is 2.
>>>>
>>>> Hope this is helpful.
>>>>
>>>> R
>>>>
>>>>
>>>>
>>>> Quoting Ryan Yan <vyan2000 at gmail.com>:
>>>>
>>>>  Hi All,
>>>>
>>>>> I was ignoring the importance of fixing the mesh size.
>>>>> For instance, if I want to compare the effect of mesh sequencing on the
>>>>> solver, I will use one level with 256 pt on each direction in 2d, in
>>>>> the
>>>>> first run.
>>>>>
>>>>> My question is,  in the second run, how to set up the number of points
>>>>> on
>>>>> the coarsest grid and pre-fix the level of the grid so that DMMG
>>>>> can bring me the exact resolution of  256 pt on each direction on the
>>>>> finest
>>>>> grid. Only this way, the two different solver are solving the problem
>>>>> of
>>>>> the
>>>>> same
>>>>> size.
>>>>>
>>>>> Thanks a lot,
>>>>>
>>>>> Yan
>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> (Rebecca) Xuefei YUAN
>>>> Department of Applied Physics and Applied Mathematics
>>>> Columbia University
>>>> Tel:917-399-8032
>>>> www.columbia.edu/~xy2102 <http://www.columbia.edu/%7Exy2102>
>>>>
>>>>
>>>>
>>>
>>
>
>
> --
> (Rebecca) Xuefei YUAN
> Department of Applied Physics and Applied Mathematics
> Columbia University
> Tel:917-399-8032
> www.columbia.edu/~xy2102
>
>
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