The mail from Rolf that didn't make it to the tools list. Begin forwarded message:
From: Rolf Rabenseifner <[email protected]> Date: October 3, 2011 4:18:09 AM MDT To: MPI3 Tools <[email protected]>, MPI-3 Fortran working group <[email protected]> Subject: Re: [MPI3 Fortran] [Mpi3-tools] Questions on the F2008 profiling interface issues Reply-To: MPI-3 Fortran working group <[email protected]>
Dear all,
according to pages:lines in https://svn.mpi-forum.org/trac/mpi-forum-web/attachment/ticket/229/mpi-repor... and the decision of the Santorini 2011 meeting, we should add the following text to accommodate the tools implementors.
P559:20-21 reads equals .FALSE.. If but should read equals .FALSE., and
After p559 the following text should be added:
---------------------------- To simplify the development of profiling libraries, the MPI routines are grouped together and it is required that if the peer routine of a group is available within an MPI library with one of its possible linker names then all of the routines in this group must be also provided according to the same linker name scheme, and if the peer routine is not available through a linker name scheme then all other routines have also not to be available through this scheme.
Peer routines and their groups: - MPI_ALLOC_MEM MPI_ALLOC_MEM and MPI_WIN_ALLOCATE. - MPI_FREE_MEM Only this routine is in this group. - MPI_GET_ADDRESS MPI_GET_ADDRESS and MPI_ADDRESS. - MPI_SEND All routines with choice buffer arguments that are not declared as ASYNCHRONOUS within the mpi_f08 module and exist already in MPI-2.2. - MPI_NEIGHBOR_ALLTOALL All routines with choice buffer arguments that are not declared as ASYNCHRONOUS within the mpi_f08 module and are new in MPI-3.0. - MPI_ISEND All routines with choice buffer arguments that are declared as ASYNCHRONOUS within the mpi_f08 module and exist already in MPI-2.2. - MPI_IBCAST All routines with choice buffer arguments that are declared as ASYNCHRONOUS within the mpi_f08 module and are new in MPI-3.0. - MPI_OP_CREATE Only this routine is in this group. - MPI_REGISTER_DATAREP Only this routine is in this group. - MPI_COMM_KEYVAL_CREATE All other routines with callback function arguments. - MPI_COMM_DUP_FN All predefined callback routines. - MPI_COMM_RANK All other MPI routines that exist already in MPI-2.2. - MPI_IBARRIER All other MPI routines that are new in MPI-3.0.
Advice to implementors. If all the following conditions are fulfilled (which is the case for most compilers) - the handles in the mpi_f08 module occupy one Fortran numerical storage unit (same as an INTEGER handle), and - the internal argument passing used to pass an actual ierror argument to a non optional ierror dummy argument is binary compatible to passing an actual ierror argument to an ierror dummy argument that is declared as OPTIONAL, and - the internal argument passing for ASYNCHRONOUS and non-ASYNCHRONOUS arguments is the same, and - the internal routine call mechanism is the same for the Fortran and the C compiler, and - the compiler does not provide TR 29113, then for most groups, the implementor may use the same internal routine implementations for all Fortran support methods with only different linker names. For TR 29113 quality, new routines are needed only for the routine groups of MPI_ISEND and MPI_IBCAST. End of advice to implementors. ----------------------------
Not directly relevant for the tools people, but giving the reason for differentiating several Choice-buffer routine groups, the following changes are also done:
P552:14-18 read - Set the INTEGER compile-time constant MPI_SUBARRAYS_SUPPORTED to .TRUE. and declare choice buffers using the Fortran 2008 TR 29113 feature assumed-type and assumed-rank, i.e., TYPE(*), DIMENSION(..), if the underlying Fortran compiler supports it. With this, non-contiguous sub-arrays can be used as buffers in nonblocking routines. but should read - Set the INTEGER compile-time constant MPI_SUBARRAYS_SUPPORTED to .TRUE. and declare choice buffers using the Fortran 2008 TR 29113 feature assumed-type and assumed-rank, i.e., TYPE(*), DIMENSION(..) in all nonblocking, split collective and persistent communication routines, if the underlying Fortran compiler supports it. With this, non-contiguous sub-arrays can be used as buffers in nonblocking routines.
Rationale. In all blocking routines, i.e., if the choice-buffer is not declared as ASYNCHRONOUS, the TR 29113 feature is not needed for the support of non-contiguous buffers because the compiler can pass the buffer by in-and-out-copy through a contiguous scratch array. End of rationale.
P555:7-10 read - Set the INTEGER compile-time constant MPI_SUBARRAYS_SUPPORTED to .TRUE. if all choice buffer arguments are declared with TYPE(*), DIMENSION(..), otherwise set it to .FALSE.. With MPI_SUBARRAYS_SUPPORTED==.TRUE., non-contiguous subarrays can be used as buers in nonblocking routines. but should read - Set the INTEGER compile-time constant MPI_SUBARRAYS_SUPPORTED to .TRUE. if all choice buffer arguments in all nonblocking, split collective and persistent communication routines are declared with TYPE(*), DIMENSION(..), otherwise set it to .FALSE.. With MPI_SUBARRAYS_SUPPORTED==.TRUE., non-contiguous subarrays can be used as buers in nonblocking routines.
I'll try to be at the tel-con today.
Best regards Rolf
----- Original Message -----
From: "Martin Schulz" <[email protected]> To: "Marc-Andre Hermanns" <[email protected]> Cc: "MPI3 Tools" <[email protected]>, "Martin Schulz" <[email protected]>, "Craig E Rasmussen" <[email protected]>, "Rolf Rabenseifner" <[email protected]>, "Jeff Squyres" <[email protected]>, "Andreas Knüpfer" <[email protected]>, "Todd Gamblin" <[email protected]>, "Tobias Hilbrich" <[email protected]>, "MPI-3 Fortran working group" <[email protected]> Sent: Sunday, October 2, 2011 6:13:46 AM Subject: Re: [Mpi3-tools] Questions on the F2008 profiling interface issues Hi Marc-Andre,
On Sep 30, 2011, at 6:27 AM, Marc-Andre Hermanns wrote:
Martin,
I was in Dresden the last few days (visiting the Vampir group, in particular Andreas Knuepfer and Tobias Hilbrich who are responsible for their MPI wrappers) and we sat down to talk about the issues around the profiling interface in ticket #229.
Here is a quick summary with a few questions that came up:
* With the new Fortran symbol naming variants, there are 6 or 8 or 10 versions for every MPI subroutine. Tools could intercept all versions by providing own symbols for all versions.
If it is clear which name the symbols have, additional symbol names should be easy to generate, so at this stage I think it doesn't matter much, whether we have 6, 8, or 10 different schemes to cover. Right?
I agree - as long as we can generate a full list of names, we can intercept them all. Adding wrappers shouldn't be a problem.
Now the problem: Within the wrapper function a tool needs to call the correct PMPI call which usually is the same prefix (either '_f08', '_f', '__' etc.) as the MPI call it is in. A mapping to matching C functions (as most tools do it now) is not possible due to problems with calling conventions for callback routines.
As far as I know our wrappers call the C routines, because we jump through all sorts of hoops to get a proper Fortran to C conversion and back. So in this regard, we need to fix this. Interestingly this has not popped up yet.
I agree - this is remarkable.
If we write Fortran wrappers in Fortran, how would a Fortran wrapper compiled with Fortran 77 have to call the C measurement code inside the wrapper? If the Fortran compiler implicitly adds underscores to the calls, do I have to provide a special Fortran interface to my measurement system then?
That is a question for the Fortran experts.
* Would the following solution work? All wrappers for Fortran are written in Fortran instead of C. [...] For every MPI function, there are 6 or 8 variants and all of them need to be provided by a tool. This would probably mean that we have to compile wrappers with all three calling conventions (mpif.h, use mpi_f and use mpi_f08) and then link them together?
Don't we need to compile with all three calling conventions on all possible compilers on a given system?
Also, here, I think the Fortran experts need to weigh in.
We currently provide all 4 name-mangling schemes with every install of Scalasca, because we had some issues with applications using two different Fortran compilers for different sub-modules. (This came up in a project some years back, and ever since then we provide all schemes in the same library and it seems to work.)
* As discussed at the forum, if we want to keep our tools in C (which is probably still the easier and better option), we need to know the symbols on the "p" side and we need a portable way to figure this out. We talked about the solution of two groups of routines - one for which we have _f08 symbols for one for which we don't. Rolf, how will you add this to the standard, in particular how will you form those groups.
I started to get some doubts about this approach. One of the issues was that some choice-buffer routines had names longer than the proposed limit. So they need to be mangled differently, especially, their symbol needs to be shortened. And as I understood it, the current idea is to leave it to the MPI implementation to define the shortened name.
I thought that was just for the argument checking in mpif.h and that we decided to not support this. Are there more locations were the names are too long?
It is one thing, finding out which suffix is used. Finding how function names are mangled without any form of restricting to possible schemes seems to be another ball game?
Am I missing something?
Yes, if we do have to shorten names, I agree - I think, though, we got around the issue, or did we not?
I think, as it was pointed out in Santorini with the Fortran Bindings in general, we (or at least I) don't have enough Fortran expertise to think this through all to the end and consider all implications. I think it would be a great benefit to have people of the Fortran WG to join on the call on Monday. I hope this is possible.
Yes, that would be great - all are cc-ed.
Martin
Cheers, Marc-Andre -- Marc-Andre Hermanns German Research School for Simulation Sciences GmbH c/o Laboratory for Parallel Programming 52056 Aachen | Germany
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________________________________________________________________________ Martin Schulz, [email protected], http://people.llnl.gov/schulzm CASC @ Lawrence Livermore National Laboratory, Livermore, USA
-- Dr. Rolf Rabenseifner . . . . . . . . . .. email [email protected] 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)
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