From: "Rolf Rabenseifner" Date: January 30, 2008 11:33:34 AM CST To: mpi-21@XXXXXXXXXXX Subject: [mpi-21] Ballot 4 - Re: Request for interpretation Reply-To: "Mailing list for discussion of MPI 2.1" This is a proposal for MPI 2.1, Ballot 4. I'm asking especially Linda Stanberry, Bill Gropp, rajeev Thakur, Dick Treumann, Raja Daoud, the participants of the email-discussion in 1999, to review this proposal. This is a follow up to: What info keys can be set? in http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/index.html with mail discussion in http://www.cs.uiuc.edu/homes/wgropp/projects/parallel/MPI/mpi-errata/discuss/infoset/ ___________________________________ Background: The sentence MPI 2.0, Sect. 4.10 Info Objects, page 43, line 38 "If a function does not recognize a key, it will ignore it, unless otherwise specified." was interpreted in two different ways: 1. This sentence is only valid in the routines in other chapters (e.g. processs creation and management, one-sided communication, parallel file I/O) where infos may be used to specify portable and implementation defined hints. 2. This interpretation is also valid for MPI_INFO_DELETE, MPI_INFO_SET, MPI_INFO_GET, and MPI_INFO_DUP. The following proposal ist based on Option 1. Option 2 is rejected due to the reason shown after the proposal. ___________________________________ Proposal: MPI 2.0, Sect. 4.10 Info Objects, page 43, line 38 read: If a function does not recognize a key, it will ignore it, unless otherwise specified. but should read: If a function in another section of the MPI standard does not recognize a key, it will ignore it, unless otherwise specified. The routines in this section. The functions in this section must not ignore any (key,value) pair. Add after MPI 2.0, Sect. 4.10 Info Objects, page 44, line 22 a new paragraph: Advice to implementors. For optimization, an MPI implementation may already sort out which (key,value) pair can be recognized for use in other chapters (e.g., in processs creation and management, one-sided communication, parallel file I/O) to guarantee a fast access to the appropriate information when used in routines of those chapters. For porpose of MPI_INFO_GET_NKEYS, MPI_INFO_GET_NTHKEY, MPI_INFO_GET_VALUELEN, and MPI_INFO_GET, the implementation must still keep also all other (key,value) pairs that cannot be recognized by that MPI implementation. (End of advice to implementors.) ________________________________ Rationale for this clarification: The first of the two interpretation options mentioned in the background information is the only valid interpretation when we assume, that layered implementation of parts of the MPI-2 standard should be possible. This was a goal of the MPI-2 Forum and the MPI-2.0 specification. ___________________________________ Comment: In the discussion (see the mails from 1999) one can clearly see, that an implementation of option 2 (done by IBM) cannot coexist with a layered implementation of MPI parallel file I/O, because MPI parallel file I/O routine need a different implementation of the INFO routines. Other chapters of MPI (e.g. 1-sided) need the original INF implementation. Two different INFO implementations cannot coexist in the same MPI library. We could see the ouutcome of such problems with MPI_Wait & co. as long as a generalized request concept was not available. ROMIO had to define non-standard MPIO_Wait & co. routines. And they persist for a long time! Without the clarification above, we have the same problem with the INFO handling. Best regards Rolf Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner@XXXXXXX 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@XXXXXXXXXXX http://lists.cs.uiuc.edu/mailman/listinfo/mpi-21