[MPICH] ROMIO practice doubts

[Rajeev Thakur]

If you have trouble getting MPD to run correctly, try debugging it as
described in Appendix A of the installation guide. If it still doesn't work,
send mail to mpich2-maint at mcs.anl.gov with details.
 
Rajeev


  _____  

From: owner-mpich-discuss at mcs.anl.gov
[mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Luiz Mendes
Sent: Monday, January 22, 2007 8:04 AM
To: mpich-discuss
Cc: Rob Ross
Subject: Re: [MPICH] ROMIO practice doubts


Hi all,
Thanks Rob,

I have been reading MPI 2 book, and other materials, and i still be in doubt
with some concepts.

There are some doubt topics that i havent learn yet.

These hints, they are effective only in non-contiguos situations, is it
right? 
romio_pvfs_listio_write and read for example, they would be effective in non
contiguous situations?

ROMIO excuses the necessity of build list_io_read function, when we use
these above hints?

And talking about Non-contiguous access, i understood it as a heterogeneous
thing. For example, in a data, we have the first 3 blocks of one type, and
the next block is a different thing with 2 blocks for example. Is it right? 

Contiguity refers to belong to a same element?

When i define an MPI_Vector for example, i set non null strides. These blank
spaces, they could be used for other elements?

I am trying to make a simple benchmark to measure bandwith, but i didnt get
it works yet. 

Non contiguouos datatypes are only these ones that have strides? if i make a
datatype that consists of a "entire line row" in each block, it could be
considered a non contiguos thing? The hints would do any influency over it? 

In MPICH2, i create a mpd.hosts file, but i am not getting it works,
mpdtrace doesnt tell anything about the slave node. What should  i do?

Thanks in advance, luiz.






2007/1/22, Rob Ross <rross at mcs.anl.gov>: 

Hi Luiz,

That's exactly where the hints go. You can also use the
MPI_File_set_info() call if you like, and you can pass hints it at
MPI_File_set_view() time as well.

Regards,

Rob

Luiz Mendes wrote: 
> Hi all,
>
> I have read MPI 2 book, ROMIO guide and some articles about
> optimizations for MPI IO. But i didnt see yet or i didnt understand
> where hints would be placed on MPI_File_open code. 
>
> Should i use ROMIO hints replaceing MPI_INFO_NULL constant in
> MPI_File_open function?
>
> Thanks in advance
> Luiz Mendes
>
>



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