[mpich-discuss] aggregator in collective I/O

[Jaln]

Thanks Rob very much,

Jialin

On Fri, Oct 17, 2014 at 9:45 AM, Rob Latham <robl at mcs.anl.gov> wrote:

>
>
> On 10/16/2014 10:07 PM, Jaln wrote:
>
>> Hi,
>> How can I know the aggregator's rank in the collective I/O?
>>
>
> fd->hints->ranklist[] contains an array of MPI ranks assigned to an
> aggregator.
>
>
>  I also feel difficult to distinguish the aggregator and non-aggregator
>> in the ad_read_coll.c,
>> for example, in function ADIOI_R_Exchange_data,
>> how can I know it is executed by a process or an aggregator?
>> I can only see how 'nprocs_for_coll' is used in partitioning the file
>> domain,
>> but couldn't see how it is used to tell the certain number of aggregator
>> to do the collective I/O.
>>
>
> I think you want to look at ADIOI_Calc_aggregator, which will report which
> MPI-IO aggregator is responsible for which regions of a file, and how much.
>
> ADIOI_R_Exchange_data is called by every process.  Some processes are
> receiving data from an aggregator, and aggregators are sending read data,
> but everyone participates.
>
> Take a look earlier on:  ADIOI_Calc_my_req and ADIOI_Calc_others_req are
> two of the routines responsible for generating the schedule of requests.
>
> ==rob
>
> --
> Rob Latham
> Mathematics and Computer Science Division
> Argonne National Lab, IL USA
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