To: Leonard Wisniewski - Sun High Performance Computing <lenbo@XXXXXXXXXXXXXXXXXXX>
cc: mpi-comments@XXXXXXXXXXXXX
Subject: Re: Two MPI I/O questions 
In-reply-to: Your message of "Thu, 21 Dec 2000 14:53:30 EST."
             <200012211953.OAA04417@XXXXXXXXXXXXXXXXXXX> Date: Thu, 21 Dec 2000 14:20:26 -0600
From: Rajeev Thakur <thakur@XXXXXXXXXXX>
Sender: owner-mpi-comments@XXXXXXXXXXXXX
Precedence: bulk

Hi Len,

>  I have two MPI I/O questions and I was hoping somebody on
>  this alias would know one or both answers.
>  
>  1) The MPI C++ bindings for SEEK_SET, SEEK_CUR, and SEEK_END
>  will conflict when used in a source file in which
>  /usr/include/fcntl.h is #include'd.  I recall seeing some
>  discussion on this topic, but I don't recall the resolution.
 
Bill Gropp has created a web page that contains information and
discussion about errors, ambiguities, and clarifications in the MPI
standard. See http://www-unix.mcs.anl.gov/~gropp/mpi/mpi-errata/ .

>  2) Shared file pointers.  We currently implement them as a
>  call to the run-time environment.  Someone has recently asked
>  me what would happen if the shared file pointer is used by
>  an MPI client-server.  In that case, a call to the run-time
>  environment would not be sufficient, since the client and
>  server may be operating on two different run-time environments.
>  The suggestion was made that the shared file pointers be
>  supported on a per-communicator basis.  Before going from 
>  per-job to per-communicator, I was wondering if anyone else
>  has thought about this and how to resolve it.  Maybe it was
>  not the intention of the spec for the shared file pointers
>  to be used in a client-server scenario.

Shared file pointers are defined on a per-file-handle basis not
per-job basis, i.e., it is shared among the processes in the
communicator passed to MPI_File_open. Hope that answers your question.

Regards,
Rajeev