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
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