[mpi-21] Ballot 4 - MPI_File_set_info update or replacement

Thu Jan 31 14:35:14 CST 2008

Dick and Rajeev, that's fine.
My word "updating" was not clear enough.
But that is what I wanted to say.
I'll put your text into the Ballot 4.

On Thu, 31 Jan 2008 13:59:24 -0600
 "Rajeev Thakur" <thakur_at_[hidden]> wrote:
>Looks ok. Maybe use "specify" instead of "mention".
> 
>   When an info object that specifies a subset of valid hints
>   is passed to MPI_FILE_SET_VIEW or MPI_FILE_SET_INFO, there 
>   will be no effect on previously set or defaulted hints that 
>   the info does not specify. 
> 
>Rajeev
>
>
>
>  _____  
>
>From: mpi-21-bounces_at_[hidden] [mailto:mpi-21-bounces_at_[hidden]] On
>Behalf Of Richard Treumann
>Sent: Thursday, January 31, 2008 1:04 PM
>To: Mailing list for discussion of MPI 2.1
>Subject: Re: [mpi-21] Ballot 4 - MPI_File_set_info update or replacement
>
>
>
>Rajeev 
>
>I think you just agreed with the interpretation I advocated. Neither the
>proposal or rationale made this at all clear to me. How about?
>
>Proposal:
>Add in MPI-2.0 Sect. 9.2.8, File Info, page 218, after line 18 the 
>following sentences:
>
>  When an info object that mentions a subset of valid hints
>   is passed to MPI_FILE_SET_VIEW or MPI_FILE_SET_INFO, there 
>   will be no effect on previously set or defaulted hints that 
>   the info does not mention. 
>   
>___________________________________
>Rationale for this clarification:
>  This text was missing. It was not clear, whether an info object
>  in MPI_FILE_SET_VIEW and MPI_FILE_SET_INFO was intended to 
>   replace only the mentioned hints or was intended to substitute
>   a complete new set of hints for the prior set.
>___________________________________
>
>Dick Treumann - MPI Team/TCEM 
>IBM Systems & Technology Group
>Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
>Tele (845) 433-7846 Fax (845) 433-8363
>
>
>mpi-21-bounces_at_[hidden] wrote on 01/31/2008 12:29:41 PM:
>
>> The intent is that if the user calls MPI_File_set_info (or 
>> MPI_File_set_view) twice, the 2nd call will only update (if 
>> possible) the key-vals passed in the 2nd call; others are 
>> unmodified. If the 2nd call passes MPI_INFO_NULL, nothing will 
>> change -- it won't nullify previously passed hints.
>>  
>> Rajeev
>>  
>> 
>> From: mpi-21-bounces_at_[hidden] [mailto:mpi-21-bounces_at_[hidden]] 
>> On Behalf Of Richard Treumann
>> Sent: Thursday, January 31, 2008 9:23 AM
>> To: Mailing list for discussion of MPI 2.1
>> Subject: Re: [mpi-21] Ballot 4 - MPI_File_set_info update or replacement
>
>> I think we have an overall ambiguity about what the "current set of 
>> hints" is. This ambiguity is evident in the question about what 
>> MPI_FILE_INFO_GET returns and in this discussion too. If an 
>> implementation supports 5 file hints then it must select a value for
>> each of these hints an MPI_FILE_OPEN. If there is an MPI_Info that 
>> stipulates 2 of the hints then how many hints are in the "current 
>> set of hints"? 2 or 5? I would say there are 5 and I think it makes 
>> sense for MPI_FILE_GET_INFO to return all 5 (key,value) pairs.
>> 
>> Two more specific points -
>> 
>> 1) I would expect that if at MPI_FILE_OPEN the implementation is 
>> given non-default hints ("A","yes") and ("B","no") and then at 
>> MPI_FILE_INFO_SET is given ("B","yes") the net effect is that hint 
>> "A" remains as set and hint "B" is altered (if possible). If there 
>> is a hint "C" which has never been mentioned it will have received a
>> default value at MPI_FILE_OPEN and the MPI_FILE_INFO_SET which does 
>> not mention "C" will leave that default unchanged.
>> 
>> Is the "clarification" saying hint "A" must return to default when 
>> MPI_FILE_INFO_SET fails to mention it? If that is the intent then I 
>> need to be convinced. If we decide this is to be blessed then we 
>> probably need to say that any use of MPI_FILE_SET_INFO must first 
>> call MPI_FILE_GET_INFO, tweek the INFO it gets back from 
>> MPI_FILE_GET_INFO and pass that to MPI_FILE_SET_INFO to avoid 
>> unexpected changes to the set of hints that is "in effect".
>> 
>> 2) Since a hint is a hint, not a command, it can be rejected. It is 
>> possible that some hint can be honored at MPI_FILE_OPEN but once it 
>> has been honored, cannot be altered at reasonable cost. 
>> 
>> For example, maybe somebody's MPI_FILE_OPEN could accept a hint 
>> ("buffer_size", "dynamic-64MB") meaning "start with a 64MB buffer 
>> but be prepared to accept changes to buffer size". If the user has 
>> set hint ("buffer_size", "64MB") at FILE_OPEN, the implelentation 
>> would omit whatever synchs are needed to preserve the ability to 
>> change on the fly. Passing ("buffer_size", "dynamic-16MB") to 
>> MPI_FILE_SET_INFO could be honored if the user had chosen "dynamic" 
>> at FILE_OPEN but would need to be ignored if he had not.
>> 
>> For most implementations, a hint like "buffer_size" could not be 
>> honored at all after the first file read or write had been done.
>> 
>> Dick Treumann - MPI Team/TCEM 
>> IBM Systems & Technology Group
>> Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
>> Tele (845) 433-7846 Fax (845) 433-8363
>> 
>> 
>> mpi-21-bounces_at_[hidden] wrote on 01/31/2008 08:24:51 AM:
>> 
>> > This is a proposal for MPI 2.1, Ballot 4.
>> > 
>> > I'm asking especially the implementors to check, whether
>> > this interpretation is implemented in their MPI implementations,
>> > or does not contradict to the existing implementation.
>> > 
>> > This is a follow up to:
>> >   MPI_File_set_info
>> >   in http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-
>> > errata/index.html
>> > with mail discussion not yet existing
>> > ___________________________________
>> > 
>> > Proposal:
>> > Add in MPI-2.0 Sect. 9.2.8, File Info, page 218, after line 18 the 
>> > following sentences:
>> > 
>> >   With MPI_FILE_SET_VIEW and MPI_FILE_SET_INFO the current setting
>> >   of all hints used by the system to this open file is updated by 
>> >   the (key,value) pairs in the info argument.
>> > ___________________________________
>> > Rationale for this clarification:
>> >   This text was missing. It was not clear, whether a info handles
>> >   in MPI_FILE_SET_VIEW and MPI_FILE_SET_INFO are updating or replacing
>> >   the current set of used hints. 
>> >   The developers from ROMIO decided to update the current set of used
>hints.
>> >   Therefore, this behavior should be the expected behavior of a majority
>> >   of users.
>> > ___________________________________
>> > 
>> > Best regards
>> > Rolf
>> > 
>> > 
>> > 
>> > 
>> > Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner_at_[hidden]
>> > High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
>> > University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
>> > Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
>> > Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)
>> > _______________________________________________
>> > mpi-21 mailing list
>> > mpi-21_at_[hidden]
>> > http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21
>> _______________________________________________
>> mpi-21 mailing list
>> mpi-21_at_[hidden]
>> http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21
>
>

Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner_at_[hidden]
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)