September 2020 - mpiwg-fortran - mailman3.cels.anl.gov

Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran?
by Jeff Squyres (jsquyres) 08 Sep '20

08 Sep '20

On Sep 8, 2020, at 11:15 AM, Rolf Rabenseifner via mpiwg-fortran <mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]>> wrote: It was clearly overseen when setting up the language interoperability chapter. Yes, we should duplicate the whole table MPI-3.1 A.1.1. p672:6-12 on MPI_STATUS_SIZE and the indexes MPI_SOURCE, MPI_TAG, and MPI_ERROR. My apologies, because I was involved. In C, I would recommend to use the following name scheme that we already use for other Fortran specific constants and functions: int MPI_F_STATUS_SIZE and MPI_F_SOURCE, MPI_F_TAG, and MPI_F_ERROR, Ah, yes: "F" is better (i.e., shorter than "FORTRAN"). (in C only to specify a Fortran status array and indexes into such an array as defined in mpif.h and the mpi module. The values of Fortran MPI_STATUS_SIZE and C MPI_F_STATUS_SIZE are identical, whereas the indexes in C are 1 less than in Fortran to reflect that the arrays in Fortran start by default with index 1 whereas in C with index 0) On MPI-3.1 p656:29, I would add In C, such an f_status array can be defined with MPI_Fint f_status[MPI_F_STATUS_SIZE]. Within this array, one can use in C the indexes MPI_F_SOURCE, MPI_F_TAG and MPI_F_ERROR to access the same elements as in Fortran with MPI_SOURCE, MPI_TAG and MPI_ERROR. The C indexes are 1 less the corresponding indexes in Fortran due to the different default array start indexes in both languages. This is better than the text I had roughed out. I'll use it; thanks. And MPI_F_STATUS_SIZE must be added to the list on page 15. Yes, and I would treat it is an Errata because of the incompletness of Section 17.2.5. And yes, sizeof(MPI_Status) may be 24 (bytes in C) whereas MPI_STATUS_SIZE and the new MPI_F_STATUS_SIZE would both be 6 (Fortran INTEGER). I'll submit an Errata PR / PDF for everyone to review shortly. -- Jeff Squyres jsquyres(a)cisco.com<mailto:[email protected]>

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Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran?
by Jeff Squyres (jsquyres) 08 Sep '20

08 Sep '20

Issue (includes 3.x and 4.0 PDFs): https://github.com/mpi-forum/mpi-issues/issues/306 * 3.x PR: https://github.com/mpi-forum/mpi-standard/pull/271 * 4.0 PR: https://github.com/mpi-forum/mpi-standard/pull/270 Please review before I send this to the main Forum list. Thanks! On Sep 8, 2020, at 11:15 AM, Rolf Rabenseifner via mpiwg-fortran <mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]>> wrote: It was clearly overseen when setting up the language interoperability chapter. Yes, we should duplicate the whole table MPI-3.1 A.1.1. p672:6-12 on MPI_STATUS_SIZE and the indexes MPI_SOURCE, MPI_TAG, and MPI_ERROR. My apologies, because I was involved. In C, I would recommend to use the following name scheme that we already use for other Fortran specific constants and functions: int MPI_F_STATUS_SIZE and MPI_F_SOURCE, MPI_F_TAG, and MPI_F_ERROR, (in C only to specify a Fortran status array and indexes into such an array as defined in mpif.h and the mpi module. The values of Fortran MPI_STATUS_SIZE and C MPI_F_STATUS_SIZE are identical, whereas the indexes in C are 1 less than in Fortran to reflect that the arrays in Fortran start by default with index 1 whereas in C with index 0) On MPI-3.1 p656:29, I would add In C, such an f_status array can be defined with MPI_Fint f_status[MPI_F_STATUS_SIZE]. Within this array, one can use in C the indexes MPI_F_SOURCE, MPI_F_TAG and MPI_F_ERROR to access the same elements as in Fortran with MPI_SOURCE, MPI_TAG and MPI_ERROR. The C indexes are 1 less the corresponding indexes in Fortran due to the different default array start indexes in both languages. And MPI_F_STATUS_SIZE must be added to the list on page 15. Yes, and I would treat it is an Errata because of the incompletness of Section 17.2.5. And yes, sizeof(MPI_Status) may be 24 (bytes in C) whereas MPI_STATUS_SIZE and the new MPI_F_STATUS_SIZE would both be 6 (Fortran INTEGER). Best regards Rolf ----- Original Message ----- From: "MPI-WG Fortran working group" <mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]>> To: "MPI-WG Fortran working group" <mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]>> Cc: "wgropp" <wgropp(a)illinois.edu<mailto:[email protected]>> Sent: Tuesday, September 8, 2020 3:43:29 PM Subject: Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran? I honestly can’t remember why we restricted MPI_STATUS_SIZE to Fortran - my best guess is one Jeff mentions, that we were maintaining the possibility that the C and Fortran statues could be a different size, and the possible confusion with sizeof(MPI_Status) is real. I’d go with a distinct name that included FORTRAN as an alternative. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Sep 8, 2020, at 8:32 AM, Jeff Squyres (jsquyres) via mpiwg-fortran < [ mailto:[email protected] | mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]> ] wrote: Question: why is MPI_STATUS_SIZE only defined in Fortran? MPI-3.1:2.5.4 p15:36 specifically states that MPI_STATUS_SIZE is only defined in Fortran. Why isn't is also defined in C? I ask because I was just writing a test for the MPI_Status conversion functions in Open MPI. The test spans both Fortran and C. But in order to test the MPI_Status_f2c / MPI_Status_c2f functions (which are only defined in C, mind you), I wanted to make a stack-allocated array of MPI_Fint's for the INTEGER-array-style Fortran status. ...but I couldn't, because MPI_STATUS_SIZE isn't defined in C. Indeed, there's no mechanism in C for knowing how long an INTEGER-style Fortran status array needs to be -- even though we have functions in C for dealing with INTEGER-style Fortran statuses. To be totally clear, you can't do this in C: MPI_Fint f_status[MPI_STATUS_SIZE]; Is this an oversight? Shouldn't we define MPI_STATUS_SIZE in all languages? Or, perhaps if there's possible confusion between MPI_STATUS_SIZE in C and sizeof(MPI_Status) (since they could actually be different values), perhaps we could call it MPI_FORTRAN_STATUS_SIZE in C? (Or even MPI_FORTRAN_INTEGER_STATUS_SIZE to differentiate it from sizeof(TYPE(MPI_Status))? Thoughts? If we view this as an errata, I think there's still time to get an update in for MPI-4. -- Jeff Squyres [ mailto:[email protected] | jsquyres(a)cisco.com<mailto:[email protected]> ] _______________________________________________ mpiwg-fortran mailing list mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran _______________________________________________ mpiwg-fortran mailing list mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran -- Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner(a)hlrs.de<mailto:[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<http://www.hlrs.de/people/rabenseifner> . Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) . _______________________________________________ mpiwg-fortran mailing list mpiwg-fortran(a)lists.mpi-forum.org<mailto:[email protected]> https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran -- Jeff Squyres jsquyres(a)cisco.com<mailto:[email protected]>

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Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran?
by Rolf Rabenseifner 08 Sep '20

08 Sep '20

It was clearly overseen when setting up the language interoperability chapter. Yes, we should duplicate the whole table MPI-3.1 A.1.1. p672:6-12 on MPI_STATUS_SIZE and the indexes MPI_SOURCE, MPI_TAG, and MPI_ERROR. My apologies, because I was involved. In C, I would recommend to use the following name scheme that we already use for other Fortran specific constants and functions: int MPI_F_STATUS_SIZE and MPI_F_SOURCE, MPI_F_TAG, and MPI_F_ERROR, (in C only to specify a Fortran status array and indexes into such an array as defined in mpif.h and the mpi module. The values of Fortran MPI_STATUS_SIZE and C MPI_F_STATUS_SIZE are identical, whereas the indexes in C are 1 less than in Fortran to reflect that the arrays in Fortran start by default with index 1 whereas in C with index 0) On MPI-3.1 p656:29, I would add In C, such an f_status array can be defined with MPI_Fint f_status[MPI_F_STATUS_SIZE]. Within this array, one can use in C the indexes MPI_F_SOURCE, MPI_F_TAG and MPI_F_ERROR to access the same elements as in Fortran with MPI_SOURCE, MPI_TAG and MPI_ERROR. The C indexes are 1 less the corresponding indexes in Fortran due to the different default array start indexes in both languages. And MPI_F_STATUS_SIZE must be added to the list on page 15. Yes, and I would treat it is an Errata because of the incompletness of Section 17.2.5. And yes, sizeof(MPI_Status) may be 24 (bytes in C) whereas MPI_STATUS_SIZE and the new MPI_F_STATUS_SIZE would both be 6 (Fortran INTEGER). Best regards Rolf ----- Original Message ----- > From: "MPI-WG Fortran working group" <mpiwg-fortran(a)lists.mpi-forum.org> > To: "MPI-WG Fortran working group" <mpiwg-fortran(a)lists.mpi-forum.org> > Cc: "wgropp" <wgropp(a)illinois.edu> > Sent: Tuesday, September 8, 2020 3:43:29 PM > Subject: Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran? > I honestly can’t remember why we restricted MPI_STATUS_SIZE to Fortran - my best > guess is one Jeff mentions, that we were maintaining the possibility that the C > and Fortran statues could be a different size, and the possible confusion with > sizeof(MPI_Status) is real. I’d go with a distinct name that included FORTRAN > as an alternative. > > Bill > > William Gropp > Director and Chief Scientist, NCSA > Thomas M. Siebel Chair in Computer Science > University of Illinois Urbana-Champaign > > > > > > > > > > On Sep 8, 2020, at 8:32 AM, Jeff Squyres (jsquyres) via mpiwg-fortran < [ > mailto:[email protected] | mpiwg-fortran(a)lists.mpi-forum.org ] > > wrote: > > Question: why is MPI_STATUS_SIZE only defined in Fortran? > > MPI-3.1:2.5.4 p15:36 specifically states that MPI_STATUS_SIZE is only defined in > Fortran. Why isn't is also defined in C? > > I ask because I was just writing a test for the MPI_Status conversion functions > in Open MPI. The test spans both Fortran and C. But in order to test the > MPI_Status_f2c / MPI_Status_c2f functions (which are only defined in C, mind > you), I wanted to make a stack-allocated array of MPI_Fint's for the > INTEGER-array-style Fortran status. ...but I couldn't, because MPI_STATUS_SIZE > isn't defined in C. Indeed, there's no mechanism in C for knowing how long an > INTEGER-style Fortran status array needs to be -- even though we have functions > in C for dealing with INTEGER-style Fortran statuses. > > To be totally clear, you can't do this in C: > > MPI_Fint f_status[MPI_STATUS_SIZE]; > > Is this an oversight? Shouldn't we define MPI_STATUS_SIZE in all languages? > > Or, perhaps if there's possible confusion between MPI_STATUS_SIZE in C and > sizeof(MPI_Status) (since they could actually be different values), perhaps we > could call it MPI_FORTRAN_STATUS_SIZE in C? (Or even > MPI_FORTRAN_INTEGER_STATUS_SIZE to differentiate it from > sizeof(TYPE(MPI_Status))? > > Thoughts? > > If we view this as an errata, I think there's still time to get an update in for > MPI-4. > > -- > Jeff Squyres > [ mailto:[email protected] | jsquyres(a)cisco.com ] > > _______________________________________________ > mpiwg-fortran mailing list > mpiwg-fortran(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran > > > _______________________________________________ > mpiwg-fortran mailing list > mpiwg-fortran(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran -- Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner(a)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: Room 1.307) .

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Status followup question: missing const's in C bindings
by Jeff Squyres (jsquyres) 08 Sep '20

08 Sep '20

It looks like we have the following 4 bindings for the status conversion functions in C: int MPI_Status_f082c(const MPI_F08_status *f08_status, MPI_Status *c_status) int MPI_Status_c2f08(const MPI_Status *c_status, MPI_F08_status *f08_status) int MPI_Status_f2f08(MPI_Fint *f_status, MPI_F08_status *f08_status) int MPI_Status_f082f(MPI_F08_status *f08_status, MPI_Fint *f_status) Shouldn't the latter 2 functions have "const" before their first parameters? -- Jeff Squyres jsquyres(a)cisco.com

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Re: [MPIWG Fortran] MPI_STATUS_SIZE: Why only in Fortran?
by William Gropp 08 Sep '20

08 Sep '20

I honestly can’t remember why we restricted MPI_STATUS_SIZE to Fortran - my best guess is one Jeff mentions, that we were maintaining the possibility that the C and Fortran statues could be a different size, and the possible confusion with sizeof(MPI_Status) is real. I’d go with a distinct name that included FORTRAN as an alternative. Bill William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign > On Sep 8, 2020, at 8:32 AM, Jeff Squyres (jsquyres) via mpiwg-fortran <mpiwg-fortran(a)lists.mpi-forum.org> wrote: > > Question: why is MPI_STATUS_SIZE only defined in Fortran? > > MPI-3.1:2.5.4 p15:36 specifically states that MPI_STATUS_SIZE is only defined in Fortran. Why isn't is also defined in C? > > I ask because I was just writing a test for the MPI_Status conversion functions in Open MPI. The test spans both Fortran and C. But in order to test the MPI_Status_f2c / MPI_Status_c2f functions (which are only defined in C, mind you), I wanted to make a stack-allocated array of MPI_Fint's for the INTEGER-array-style Fortran status. ...but I couldn't, because MPI_STATUS_SIZE isn't defined in C. Indeed, there's no mechanism in C for knowing how long an INTEGER-style Fortran status array needs to be -- even though we have functions in C for dealing with INTEGER-style Fortran statuses. > > To be totally clear, you can't do this in C: > > MPI_Fint f_status[MPI_STATUS_SIZE]; > > Is this an oversight? Shouldn't we define MPI_STATUS_SIZE in all languages? > > Or, perhaps if there's possible confusion between MPI_STATUS_SIZE in C and sizeof(MPI_Status) (since they could actually be different values), perhaps we could call it MPI_FORTRAN_STATUS_SIZE in C? (Or even MPI_FORTRAN_INTEGER_STATUS_SIZE to differentiate it from sizeof(TYPE(MPI_Status))? > > Thoughts? > > If we view this as an errata, I think there's still time to get an update in for MPI-4. > > -- > Jeff Squyres > jsquyres(a)cisco.com > > _______________________________________________ > mpiwg-fortran mailing list > mpiwg-fortran(a)lists.mpi-forum.org > https://lists.mpi-forum.org/mailman/listinfo/mpiwg-fortran

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MPI_STATUS_SIZE: Why only in Fortran?
by Jeff Squyres (jsquyres) 08 Sep '20

08 Sep '20

Question: why is MPI_STATUS_SIZE only defined in Fortran? MPI-3.1:2.5.4 p15:36 specifically states that MPI_STATUS_SIZE is only defined in Fortran. Why isn't is also defined in C? I ask because I was just writing a test for the MPI_Status conversion functions in Open MPI. The test spans both Fortran and C. But in order to test the MPI_Status_f2c / MPI_Status_c2f functions (which are only defined in C, mind you), I wanted to make a stack-allocated array of MPI_Fint's for the INTEGER-array-style Fortran status. ...but I couldn't, because MPI_STATUS_SIZE isn't defined in C. Indeed, there's no mechanism in C for knowing how long an INTEGER-style Fortran status array needs to be -- even though we have functions in C for dealing with INTEGER-style Fortran statuses. To be totally clear, you can't do this in C: MPI_Fint f_status[MPI_STATUS_SIZE]; Is this an oversight? Shouldn't we define MPI_STATUS_SIZE in all languages? Or, perhaps if there's possible confusion between MPI_STATUS_SIZE in C and sizeof(MPI_Status) (since they could actually be different values), perhaps we could call it MPI_FORTRAN_STATUS_SIZE in C? (Or even MPI_FORTRAN_INTEGER_STATUS_SIZE to differentiate it from sizeof(TYPE(MPI_Status))? Thoughts? If we view this as an errata, I think there's still time to get an update in for MPI-4. -- Jeff Squyres jsquyres(a)cisco.com

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