[Mpi-forum] MPI-3: MPI_T_ERR_... and MPI_ERR_LASTCODE

Sun Jul 22 18:23:40 CDT 2012

Hi Rolf, all,

I thought we had discussed the error semantics of MPI_T in several meetings/readings and nobody objected, but I generally agree with your comments below. However, they are not really error classes (at least in the tools group we/I never thought about them this way), but just well defined return codes. Nevertheless, they fit the model and semantics of classes and hence should integrated into the same rules for consistency. I also agree with Bronis, though, that larger feedback on this would be good to avoid errors because of rushing it.

To keep changes minimal, I would suggest that we only change the following sentence, which IMHO is sufficient (and would essentially follow option b):

All return codes with the prefix MPI_T_ must be unique values and cannot overlap with any other return values returned by the MPI implementation. Further, they shall be treated as MPI error classes as defined in Chapter 8.4 and follow the same rules and restrictions.

This would also make changes in the appendix unnecessary.

As for making MPI_ERROR_CLASS and MPI_ERROR_STRING callable before Init (and then also after finalize), yes that would be very useful, but is a general issue not only related to MPI_T. If we decide this is too invasive at this point, I would like to see this at least in 3.1.

Martin

On Jul 22, 2012, at 1:46 PM, Rolf Rabenseifner wrote:

> About 1. question:
> 
> I changed the headers of the three error code tables in the Annex
> according to Tables 8.1 and 8.2 from "Return codes"
> into "Error classes".
> 
> svn r1505: I used also "Error classes" for the tools table
> svn r1507: I went back to the official ticket 266 text "Return codes"
> 
> The Tools group should decide whether 
> a. they want to stay with special return codes that are not 
>  part of the rule in Set. 8.4
> 
>   0 = MPI_SUCCESS < MPI_ERR_... <= MPI_ERR_LASTCODE
> 
>  In this case they should change "return code" 
>  into "error codes are returned" plus noting that
>  the routine MPI_ERROR_STRING can be applied
>  with the open question, whether MPI_EEROR_STRING
>  can be applied before a call to MPI_INIT.
> 
>  Similar problem with failed MPI_INIT and analysing its
>  returned error code:
>  One needs at least MPI_ERROR_CLASS and MPI_ERROR_STRING
>  callable before MPI_INIT.
> 
> b. or you may use the same terminology as in Sect. 8.4,
>  then new table 14.5 must show "Error classes".
> 
>  In this case you should integrate the MPI_T_ERR_...
>  into the MPI_ERR_LASTCODE rule.
> 
>  You need at least MPI_ERROR_CLASS and MPI_ERROR_STRING
>  callable before MPI_INIT.
> 
> I would prefer solution b together combined with the
> minimal solution for failed MPI_INIT, i.e.,
> adding MPI_ERROR_CLASS and MPI_ERROR_STRING to
> the list of routines callable outside of MPI's 
> initialization.
> 
> 
> About 2. question: MPI_T_ERR_CANTINIT -_> MPI_T_ERR_CANNOTINIT
> 
> svn r1506: done by Bronis in chap-tools/mpit.tex
> svn r1508: done by Rolf in chap-appLang/appLang-Const.tex
> 
> Rolf
> 
> ----- Original Message -----
>> From: "Bronis R. de Supinski" <bronis at llnl.gov>
>> To: "Main MPI Forum mailing list" <mpi-forum at lists.mpi-forum.org>
>> Cc: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
>> Sent: Sunday, July 22, 2012 10:03:44 PM
>> Subject: Re: [Mpi-forum] MPI-3: MPI_T_ERR_... and MPI_ERR_LASTCODE
>> Rolf:
>> 
>> OK, I am changing MPI_T_ERR_CANTINIT to MPI_T_ERR_CANNOTINIT.
>> 
>> As said before, we need more opinions on the first question.
>> 
>> Bronis
>> 
>> 
>> On Sun, 22 Jul 2012, Bronis R. de Supinski wrote:
>> 
>>> 
>>> Rolf:
>>> 
>>> Re:
>>>> Dear Bronis, Martin, Dave, and Kathryn,
>>>> (Profiling/Tools chapter responsibles)
>>>> 
>>>> (you may forward this to the tools list - I'm not on that list)
>>>> 
>>>> Two important questions:
>>>> 
>>>> 1. Alexander Supalov detected that we did it wrong:
>>>> The MPI_T_ERR_... list must be part of the total error
>>>> list and sorted in before MPI_ERR_LASTCODE.
>>>> 
>>>> I will change this in chap-appLang/appLang-Const.tex
>>>> 
>>>> Please look, if there must be some additional wording on this.
>>>> For example, the last sentence of Section 14.3.9
>>>> 
>>>> "All return codes with the prefix MPI_T_ must be unique values and
>>>>  cannot overlap with any other return values returned by the MPI
>>>>  implementation."
>>> 
>>> The above wording clearly states that the return values
>>> should be consistent with MPI_ERR_* return values. So,
>>> either the above wording needs to change (I do not see
>>> why MPI_T_* return values need to be distinct from
>>> MPI_ERR_* return values since the user should know that
>>> they were using an MPI_T_* function) or we need to adopt
>>> something like what you suggest.
>>> 
>>> I think we need broader opinions to make the decision.
>>> 
>>> I am concerned that wrapping up the document for MPI 3.0
>>> has led to a fast and loose attitude about making broader
>>> changes "in order to get it done." This attitude can
>>> easily lead to suboptimal solutions.
>>> 
>>> Bronis
>>> 
>>> 
>>> 
>>>> may be modified into
>>>> 
>>>> "All return codes with the prefix MPI_T_ must be unique values and
>>>>  cannot overlap with any other return values returned by the MPI
>>>>  implementation and satisfy
>>>> 
>>>>   0 = MPI_SUCCESS < MPI_T_ERR_... <= MPI_ERR_LASTCODE. "
>>>> 
>>>> or
>>>>   0 = MPI_SUCCESS < MPI_ERR_... < MPI_T_ERR_... <=
>>>>   MPI_ERR_LASTCODE.
>>>> 
>>>> or
>>>>   0 = MPI_SUCCESS < MPI_ERR_... <= MPI_ERR_LASTCODE <
>>>>   MPI_T_ERR_... <= MPI_T_ERR_LASTCODE.
>>>> 
>>>> and the MPI_ERR_LASTCODE and/or MPI_T_ERR_LASTCODE may be also
>>>> repeated
>>>> in Table 14.5 as last entry, as done for the first value
>>>> MPI_SUCCESS.
>>>> 
>>>> This proposal is based on Section 8.4, the sentence
>>>> 
>>>> "The error codes satisfy,
>>>>   0 = MPI_SUCCESS < MPI_ERR_... <= MPI_ERR_LASTCODE: "
>>>> 
>>>> Please confirm, that Alexander is right,
>>>> please include me in your discussion and
>>>> please tell me your result
>>>> that I can do the correct changes in chap-appLang
>>>> and you in chap-tools.
>>>> 
>>>> 2. Qeustion is less important; it is about naming:
>>>> Alexander also noticed that your names do not fit to the names
>>>> used in the past:
>>>> 
>>>> MPI_T_ERR_CANTINIT --> MPI_T_ERR_CANNOTINIT (we do not use
>>>> abbrevations)
>>>> 
>>>> or
>>>> 
>>>> MPI_T_ERR_CANTINIT --> MPI_T_ERR_CANNOT_INIT (we do not use
>>>> abbrevations)
>>>> 
>>>> In most cases, we do not combine words without underscore.
>>>> 
>>>> As far as I see, you can do the underscores.
>>>> Be sure to stay at maximum with 30 characters.
>>>> 
>>>> Current longest MPI_T constants:
>>>> 
>>>> 123456789012345678901234567890
>>>> MPI_T_PVAR_CLASS_HIGHWATERMARK
>>>> MPI_T_PVAR_CLASS_LOWWATERMARK
>>>> MPI_T_VERBOSITY_MPIDEV_DETAIL
>>>> 
>>>> Based on this, I would stay with you names based on your MPI_T
>>>> rule:
>>>> MPI_T_<structual-areas-with-underscores>_<final-name-without-underscores>
>>>> 
>>>> i.e., I would only change
>>>> 
>>>> MPI_T_ERR_CANTINIT --> MPI_T_ERR_CANNOTINIT
>>>> 
>>>> Please tell me also your decision
>>>> that I can do the correct changes in chap-appLang
>>>> and you in chap-tools.
>>>> 
>>>> Best regards
>>>> Rolf
>>>> 
>>>> 
>>>> --
>>>> Dr. Rolf Rabenseifner . . . . . . . . . .. email
>>>> rabenseifner at hlrs.de
>>>> 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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>>> 
> 
> -- 
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> 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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________________________________________________________________________
Martin Schulz, schulzm at llnl.gov, http://people.llnl.gov/schulzm
CASC @ Lawrence Livermore National Laboratory, Livermore, USA