[mpas-developers] derived data type redesign

Todd Ringler ringler at lanl.gov
Tue Dec 20 12:09:11 MST 2011

Hi Michael,

I was thinking about this issue this morning and if we would have the opportunity to make these DDTs more flexible in how we use them.

I think the attachment might be missing from the original email.


On Dec 20, 2011, at 12:07 PM, Michael Duda wrote:

> Hi, All.
> Attached is a first draft of a requirements and design document for the
> first item from the meeting between Doug, Conrad, and I last week; I've
> attached a PDF as well as the Latex source for editing. My assessment is
> that the changes to the DDTs themselves should be simple -- it's the
> remaining items on the list, below, that will be tricky. 
> Cheers,
> Michael
> On Wed, Dec 14, 2011 at 03:47:35PM -0700, Michael Duda wrote:
>> Hi, Doug and Conrad.
>> Here are the key development issues that we identified this morning, in
>> roughly the order we'll probably need to tackle them:
>> 1) Update/extend the fundamental derived types in mpas_grid_types.F. 
>>   In order for other parts of the infrastructure to handle multiple 
>>   blocks per task in a clean way, we'll need to be able to pass a head 
>>   pointer to a field into a routine, and have that routine loop through 
>>   all blocks for that field, with information about which cells/edges/vertices 
>>   in that field need to be communicated. 
>> 2a) Decide on a new MPAS I/O abstraction layer, which will provide a
>>   high-level interface to the PIO layer for the rest of MPAS. This layer
>>   should work with blocks of fields, and make it possible to define an
>>   arbitrary set of I/O streams at run-time.
>> 2b) Add a new module to parse a run-time I/O configuration file that
>>   will describe which fields are read or written to each of the I/O
>>   streams that a user requests via the file. This module will make calls 
>>   to the new MPAS I/O layer to register the requested fields for I/O in 
>>   the requested streams.
>> 3) Update the mpas_dmpar module to support communication operations on
>>   multiple blocks per task. This will likely involve revising the 
>>   internal data structures used to define communication of cells 
>>   between tasks, and also require revisions to the public interface 
>>   routines themselves.
>> 4) Modify the block_decomp module to enable a task to get a list of
>>   cells in more than one block that it is to be the owner of.  
>>   Implemented in the simplest way, there could simply be a namelist 
>>   option to specify how many blocks each task should own, and the 
>>   block_decomp module could look for a graph.info.part.n file, with 
>>   n=num_blocks_per_task*num_tasks, and assign blocks k, 2k, 3k, ...,
>>   num_blocks_per_task*k to task k.
>> Some of the changes, e.g., to the dmpar module, are significant enough
>> that we should consider whether a general re-write of the module would
>> be appropriate; in such cases, we should consider whether the code can
>> be made more concise and more maintainable if it were written in C.
>> Michael
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