<html><body>
<p>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.<br>
<br>
Two more specific points -<br>
<br>
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.<br>
<br>
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".<br>
<br>
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. <br>
<br>
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.<br>
<br>
For most implementations, a hint like "buffer_size" could not be honored at all after the first file read or write had been done.<br>
<br>
Dick Treumann - MPI Team/TCEM <br>
IBM Systems & Technology Group<br>
Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601<br>
Tele (845) 433-7846 Fax (845) 433-8363<br>
<br>
<br>
<tt>mpi-21-bounces@cs.uiuc.edu wrote on 01/31/2008 08:24:51 AM:<br>
<br>
> This is a proposal for MPI 2.1, Ballot 4.<br>
> <br>
> I'm asking especially the implementors to check, whether<br>
> this interpretation is implemented in their MPI implementations,<br>
> or does not contradict to the existing implementation.<br>
> <br>
> This is a follow up to:<br>
> MPI_File_set_info<br>
> in <a href="http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-">http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-</a><br>
> errata/index.html<br>
> with mail discussion not yet existing<br>
> ___________________________________<br>
> <br>
> Proposal:<br>
> Add in MPI-2.0 Sect. 9.2.8, File Info, page 218, after line 18 the <br>
> following sentences:<br>
> <br>
> With MPI_FILE_SET_VIEW and MPI_FILE_SET_INFO the current setting<br>
> of all hints used by the system to this open file is updated by <br>
> the (key,value) pairs in the info argument.<br>
> ___________________________________<br>
> Rationale for this clarification:<br>
> This text was missing. It was not clear, whether a info handles<br>
> in MPI_FILE_SET_VIEW and MPI_FILE_SET_INFO are updating or replacing<br>
> the current set of used hints. <br>
> The developers from ROMIO decided to update the current set of used hints.<br>
> Therefore, this behavior should be the expected behavior of a majority<br>
> of users.<br>
> ___________________________________<br>
> <br>
> Best regards<br>
> Rolf<br>
> <br>
> <br>
> <br>
> <br>
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@hlrs.de<br>
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530<br>
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832<br>
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner<br>
> Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)<br>
> _______________________________________________<br>
> mpi-21 mailing list<br>
> mpi-21@cs.uiuc.edu<br>
> <a href="http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21">http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21</a><br>
</tt></body></html>