[Mpi3-ft] MPI_INIT_THREAD and MPI_Failhandler_set/get_mode at MPI initialization

TERRY DONTJE terry.dontje at oracle.com
Wed Jan 18 08:32:01 CST 2012


I think the idea is worthwhile but it really smells similar to the 
defunct assertion ticket.  I really find piggy-backing the ft, cancel 
and any_source modes onto the required/provided bits a little unpleasing 
to my senses.  The reason I am displeased with the proposal is it seems 
to slightly open a door to give an application the ability to give hints 
and if we are going to do that we might as well open the door fully and 
allow vendor specific hints.  Doing the latter will require more than 
the require/provided bits.

The above aside, if the proposal is passed I guess my only other comment 
is the of moving the MPI_INIT_THREAD & MPI_QUERY_THREAD to 8.7 (startup) 
seems odd to me.   I guess I can see the reasoning of moving the 
interface to the Startup section but then the threadsafety portion of 
12.4.3 section seems to stick out strangely IMO.

--td

On 1/17/2012 5:31 AM, Rolf Rabenseifner wrote:
> Dear committees of
>   - FT,
>   - MPI_Init -->  8. Environmental Management,
>   - MPI_Init_thread -->  12. External Interfaces.
>
> Before discussing details, I would like to get a clear answer
> whether you believe that the proposal below is a good or bad idea.
>
> As already mentioned at the Jan. 2012 meeting, I would like to propose
> that the FT group may substitute the unclear collective behavior
> of MPI_Failhandler_set_mode by adding the mode to the MPI initialization.
>
> For this, I added a proposal to slide 4 in
> MPI_Forum_Overview_MPI-3.0_Jan2012_action-items.ppt
> (see my previous mail to the MPI-Forum list)
>
> - If appropriate, a new ticket that enhances MPI_INIT_THREAD
>     -- Required and provided as “bit vector” of "bit-wise OR" of
>            required_/provided_threadsafety
>          | required_/provided_ft_mode
>          | required_/provided_cancel_mode
>          | required_/provided_any_source_mode
>     -- New mask-constants MPI_THREAD_MASK, MPI_FT_MASK,
>                           MPI_CANCEL_MASK, MPI_ANY_SOURCE_MASK
>     -- With existing values for required_/provided_threadsafety
>         MPI_THREAD_SINGLE, MPI_THREAD_FUNNELED,
>         MPI_THREAD_SERIALIZED, and MPI_THREAD_MULTIPLE.
>     -- With new values for
>         - required_/provided_ft_mode =
>             MPI_FT_NONE=0, or
>             MPI_FT_FAILHANDLER_MODE_ALL≠0, or
>             MPI_FT_FAILHANDLER_MODE_SUBSET≠0, or
>         - required_/provided_cancel_mode =
>             MPI_CANCEL_ALLOWED=0, or
>             MPI_NO_CANCEL≠0
>         - required_/provided_any_source_mode =
>             MPI_ANY_SOURCE_ALLOWED=0, or
>             MPI_NO_ANY_SOURCE≠0
>     -- Values must be set identical for all processes in an MPI_COMM_WORLD
>         - It is easier to relax about this in further versions of MPI
>           than to relax already now and to restrict later
>           as now done in ticket #222 for required_/provided_threadsafety
>         - For each of the for "variables", a different decision
>           can be done.
>     -- At least for required_/provided_cancel_mode and
>        ...any_source_mode, I would require that the provided
>        value must be identical to the required value.
>        Reason: Internally, the value can be ignored.
>     -- For required_/provided_ft_mode, I would recommend
>        to allow that provided_ft_mode must be
>         - identical to required_ft_mode or MPI_FT_NONE
>         - and the same in all processes.
>     -- MPI_INIT_THREAD&  MPI_QUERY_THREAD moves
>          - from 12.4.3 (External Interfaces)
>          - to 8.7 (Startup)
>          - but explanations to ...threadsafety | ...ft_mode |
>            ...cancel_mode | ...any_source_mode are kept or written
>            in the appropriate sections 12.4.3, new 17.5 (FT Environm.),
>            3.8.4 (Cancel), 3.2.4 (Blocking Receive)
>     -- A call to MPI_INIT is identical to MPI_INIT_THREAD with
>          - the rules in 12.4.3 about required_/provided_threadsafety
>          - required_/provided_ft_mode     = MPI_FT_NONE,
>          - required_/provided_cancel_mode = MPI_CANCEL_ALLOWED,
>          - required_/provided_any_source_mode = MPI_ANY_SOURCE_ALLOWED
>     -- This ticket would have the following properties:
>          - It is clearly source-code and ABI backward compatible,
>            because
>             - the values of MPI_THREAD_SINGLE, _FUNNELED, ...
>               need not to be changed and MPI_THREAD_SINGLE need
>               not to be zero;
>             - the values representing the current MPI-2.2 quality
>               are set to zero: MPI_FT_NONE=0,
>               MPI_CANCEL_ALLOWED=0, and MPI_ANY_SOURCE_ALLOWED=0
>             - It is very unlikely that an implementation has used
>               more than 24 different bits in these 4 integer
>               constants MPI_THREAD_SINGLE, ... _MULTIPLE.
>               Therefore MPI_THREAD_MASK would have a maximum
>               of 24 bits. Enough room for the 4 bits needed
>               together for the other three ..._MASKs.
>           - FT can be switched on or off at the MPI initialization
>             and is switched off in unchanged applications.
>             Therefore no backward-compatibility-problem with a
>             modified behavior of the default error handlers
>             when FT is switched on.
>           - Normally there should be enough bit-space for further
>             decisions at MPI initialization.
>           - The decisions about the cancel and any_source
>             values would be done in different tickets
>           - FT quality is optional if we add the
>             rule that provided_ft_mode may be identical
>             to required_ft_mode ***or*** MPI_FT_NONE
>           - This rule can be changed in a further version of MPI
>             without backward-compatibility-problems.
>
> I would like to get a reply from
>   - the FT group
>   - the chapter committee of MPI_Init -->  8. Environmental Manag.
>     George Bosilca(c), Josh Hursey, Terry Dontje
>   - the chapter committee of MPI_Init_thread -->  12. External Interf.
>     Bronis R. de Supinski(c), Pavan Balaji
>
> Before discussing details, I would like to get a clear answer
> whether you believe that this is a good or bad idea.
>
> Best regards
> Rolf
>

-- 
Oracle
Terry D. Dontje | Principal Software Engineer
Developer Tools Engineering | +1.781.442.2631
Oracle *- Performance Technologies*
95 Network Drive, Burlington, MA 01803
Email terry.dontje at oracle.com <mailto:terry.dontje at oracle.com>



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