[FLASH-USERS] Guardcells filling with PARAMESH4 data/grid structure

[Anshu Dubey]

Dear Marco,

Grid_fillGuardCells is a global operation which replaces the current values
in the guard cells of
all blocks with values from interior cells of the neighboring blocks. When
you get a pointer to a block
you get access to all the variables in the block. In general, you should
only be changing the
interior cells in the block because the next call to guard cell fill will
destroy the values you
might have put in the guard cells. Any time you get a block through
Grid_getBlkPtr, you
should explicitly release it using Grid_releaseBlkPtr when you are done
with it.

The one exception to the above scenario is in the use of active particles
where mass of the
particles is mapped to their surrounding cells and some of those cells may
be guard cells.
A part of the routine Grid_mapParticlesToMesh makes sure that the values in
guard cells
are communicated back to appropriate blocks, in what we call the reverse
guard cell fill.

I hope that answers your basic question, please send me more details if you
have a specific
problem/approach in mind.

Anshu

On Fri, Feb 17, 2012 at 11:12 AM, Marco Mazzuoli <marco.mazzuoli at unige.it>wrote:

>
>     Dear all,
>
> I am working on the FLASH code implementing the PARAMESH4 data/grid
> structure.
> Could you clarify me some questions concerning the GuardCells (GC) filling?
>
> I explain the problem:
> In order to work on such a local block (with for example 4 GC) I get the
> pointer to that block with the subroutine "Grid_getBlkPtr".
> Then I could assign a new value to some GC variables.
> Finally I call the subroutine "Grid_fillGuardCells".
>
> My questions are:
> I)  What happens to GC values I had changed?
> II) Can I only read GC variables (like boundary conditions) or also write
> permanently a new value?
>
> In other words:
> i)   Which variable I'm really pointing with "Grid_getBlkPtr"?
> ii)  What I change indeed when I work on the GC of that pointer?
> iii) Do GC communicate straightforwardly to the adjacent block?
>
> Thank you to everybody.
>
> Sincerely,
>     Marco Mazzuoli
>
>
>
> Ing. Marco Mazzuoli
> Dipartimento di Ingegneria
> delle Costruzioni, dell'Ambiente e
> del Territorio (DICAT)
> via Montallegro 1
> 16145 GENOVA-ITALY
> tel.  +39 010 353 2497
> cell. +39 338 7142904
> e-mail marco.mazzuoli at unige.it
>        marco.mazzuoli84 at gmail.com
>
>
>
>
>


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Anshu Dubey
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