[pooma-dev] FW: Questions about data in Fields

[Scott Haney]

Hi Dave,

The data in fields is not necessarily continuous. We allocate based on a 
vertex-centered domain for all subfields. This is done so that when the 
field is partitioned, all of the subfields will be aligned. This fixes 
the nasty problems we had in R1 with slightly different sized fields 
giving dramatically different partitionings. This improves robustness 
and should improve performance. Note as well that if you are looking at 
a patch and there are internal guard layers, the data won't be 
continuous either.

Your best bet is to assign the patch data to a brick-array of the 
correct size. This will make the data continuous. However, it would be 
helpful to see a snippet showing exactly what you're trying to do. This 
would also help with respect to the size question - I am surprised by 
the behavior you're reporting.

Scott

On Tuesday, July 24, 2001, at 01:24 PM, William Nystrom wrote:

> Hi Guys,
>  
> I talked to Jim about interfacing to some fortran linear solver code 
> awhile back and then before I left for
> vacation, John and I did some work to try and write the interface for 
> our application using Pooma 2 so
> we could use this fortran linear solver package.  One of the things I 
> am trying to do is to query a Pooma 2
> Field and find out the size of the data that is local to a processor.  
> I've done this query for the domain object
> for a Field and for a cell centered field, it reports sizes in each 
> dimension or coordinate that are one more
> than they should be.  John told me that you guys had decided to 
> allocate enough space for a vertex centered
> field even if the field was cell centered - as an optimization of some 
> sort.  I am worried that the data for a
> cell centered field may not be contiguous because of the extra padding 
> that occurs for cell centered fields
> and because the domain object thinks it's size in each dimension is one 
> larger.  Can you tell me if the data
> for a cell centered field that is local to a processor with one patch 
> per processor is actually contiguous in
> memory?  I can test this experimentally but I have not had a chance to 
> do this yet.  Also, can you tell me the
> recommended way to get the correct size of my data on a local processor 
> for a cell centered Pooma 2
> Field?
>  
> Please send replies to sunsetmesa at earthlink.net as I am not able right 
> now to read my lanl email and I
> am not subscribing to pooma-dev from my ISP account.

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