Re: [MPIWG Fortran] Question about MPI_Status_f2f08() and _f082f()
One more update -- changelog entry added: https://github.com/mpi-forum/mpi-standard/files/4965729/mpi40-report-243eb86... In particular, look at: - page 755: lines 15 and 16 - page 756: new Fortran bindings for both functions - page 907: lines 15 and 19 - page 909: lines 27-29 If this seems ok, I'll make the corresponding MPI-3.1 errata PR. The goal will be to render (mostly?) the same as the v4.0 errata, but the back-end Latex will be different (because the mpi-4.x branch was Pythonized).
On Jul 20, 2020, at 3:02 PM, Jeff Squyres (jsquyres) via mpiwg-fortran <[email protected]> wrote:
Fortran WG:
Ok, we have all the updates now. Can you please review the LaTeX and the rendered PDF?
MPI-4.0 PR is here: https://github.com/mpi-forum/mpi-standard/pull/255
Rendered PDF from that PR is here: https://artprodcus3.artifacts.visualstudio.com/A2828b64d-12fe-4a97-80aa-ee05...
In particular, look at:
- page 755: lines 15 and 16 - page 756: new Fortran bindings for both functions - page 907: lines 15 and 19
On Jul 16, 2020, at 3:35 PM, Jeff Squyres (jsquyres) via mpiwg-fortran <[email protected]> wrote:
I just filed the issue:
https://github.com/mpi-forum/mpi-issues/issues/298
And a first cut of the MPI-4.x PR:
https://github.com/mpi-forum/mpi-standard/pull/255
I just added a statement in the text on the PR so far. I need to work with Martin R to get the Pythonization changes.
I'll post back here when we have something for everyone to review.
After that, we'll make a corresponding equivalent-looking PR for MPI-3.x.
On Jul 16, 2020, at 12:07 PM, Rolf Rabenseifner <[email protected]> wrote:
Good idea.
With the pythonizing, we have the additional header Fortran binding which could be substituted by Fortran binding (the following procedure is not available with mpif.h)
And in A.4.12 we could write in front of the two routines also
The following procedure is not available with mpif.h:
I would not use the positive statement "only available in the mpi module", because the procedure itself is in mpi_f08 and mpi, and only this specific Interface only in the mpi module.
I would use "with mpif.h" and not use "in mpif.h", because most/all MPI libraries do not provide procedure interfaces in mpif.h.
Best regards Rolf
----- Original Message -----
From: "wgropp" <[email protected]> To: "MPI-WG Fortran working group" <[email protected]> Cc: "Rolf Rabenseifner" <[email protected]>, "Jeff Squyres" <[email protected]> Sent: Thursday, July 16, 2020 5:17:55 PM Subject: Re: [MPIWG Fortran] Question about MPI_Status_f2f08() and _f082f()
Adding something to the MPI_Status_f2f08/f082f bindings to specify these are only for the MPI module is a good idea.
Bill
William Gropp Director and Chief Scientist, NCSA Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign
On Jul 16, 2020, at 9:19 AM, Jeff Squyres (jsquyres) via mpiwg-fortran <[email protected]> wrote:
Thanks Rolf, Hubert, and Bill. It all makes sense.
Rolf has proposed that we add the following at the end of the sentence on MPI-3.1 p657 line 11:
(only in the mpi_f08 and mpi modules)
This sounds reasonable to me, but do we need some additional annotation in the MPI_Status_f2f08 and _f082f bindings to indicate that the all-caps Fortran binding is only for the mpi module, and not mpif.h?
On Jul 15, 2020, at 3:08 PM, Rolf Rabenseifner via mpiwg-fortran <[email protected]> wrote:
Dear Hubert and Jeff,
Ø I'm a little curious as to why we conspicuously left it out of mpif.h.
I expect, we didn't want that mpif.h must include the overloading of the operators .NE. and .EQ. for all TYPE(MPI_....). I'm not sure whether such declaration is allowed outside of a module.
The use of mpif.h was already deprecated, i.e., if somebody wants to use mpi_f08 stuff in old code, he or she must first substitute the include mpif.h by use mpi.
... But it was never intended that the programmer does this transformation within the old Fortran subroutine (and old Fortran 77 compiler or using Fortran 77 language kind wouldn’t support Type(MPI_Status) in mpif.h).
It was intended that you can convert from old INTEGER variable or array to new TYPE(MPI_...) within source code using the mpi module or using the mpi_f08 module.
But we excluded mpif.h because it need not to provide compile-time argument checking and it use is therefore "strongly discouraged". Why should we add something to this "strongly discouraged" mpif.h area.
And, to add it in a later version of MPI is simple. To remove it later is not backward compatible. This may be another reason for not adding it to mpif.h
Best regards Rolf
----- Original Message -----
From: "MPI-WG Fortran working group" <[email protected]> To: "MPI-WG Fortran working group" <[email protected]> Cc: "Hubert Ritzdorf" <[email protected]> Sent: Wednesday, July 15, 2020 6:15:58 PM Subject: Re: [MPIWG Fortran] Question about MPI_Status_f2f08() and _f082f()
Ø I'm a little curious as to why we conspicuously left it out of mpif.h.
When I remember correctly, MPI_Status_f2f08() and _f082f() subroutines were for a smooth transition from Fortran 77 to Fortran 08.
I.e. if a programmer has changed some functions from old Fortran to Fortran 08 and uses other libraries or subroutines which still use the old Fortran status as input or output argument, it was possible to transfer the old Fortran status within the Fortran 08 subroutine. But it was never intended that the programmer does this transformation within the old Fortran subroutine (and old Fortran 77 compiler or using Fortran 77 language kind wouldn’t support Type(MPI_Status) in mpif.h).
Hubert
From: mpiwg-fortran [mailto:[email protected]] On Behalf Of Jeff Squyres (jsquyres) via mpiwg-fortran Sent: Wednesday, July 15, 2020 5:26 PM To: MPI Fortran WG <[email protected]> Cc: Jeff Squyres (jsquyres) <[email protected]> Subject: Re: [MPIWG Fortran] Question about MPI_Status_f2f08() and _f082f()
Just to bring this thread back on-track about TYPE(MPI_Status)...
Off list, I asked Rolf R. about this issue -- he cited the same things I did, plus a few more:
On your question on TYPE(MPI_Status), TYPE(MPI_Comm), ...:
MPI-3.1
- page 607 lines 18-24 require these types and the overloaded
operators .EQ./.NE. for mpi_f08 module
- page 609 lines 34-36 require these types and the overloaded
operators .EQ./.NE. for mpi module
- there is no such text on page 611-612 on mpif.h
And page 802 lines 9-15 also Show that it was never intented to add
These types anf routines to old mpif.h.
It would be helpful, to add at least on page 657 line 11
C, some in both C and Fortran (only in the mpi_f08 and mpi modules).
Can you fix this with an one-vote-bug-fix-issue?
Because it is not good if the information must be taken from the change-log.
---
Summary:
Does this mean that TYPE(MPI_Status)
[ and the Fortran routines MPI_STATUS_F2F08 and _F082F ]
needs to be defined in
- mpif.h? NO
- and the mpi module? YES
Bug-fix needed in MPI-3.1 page 657 line 11: add
"(only in the mpi_f08 and mpi modules)" at the end.
I hope this helps.
Best regards
Rolf
So I think there's at least a clarification here: the TYPE(MPI_Status) and associated functions is -- at a minimum -- supposed to be in the mpi module.
I'm a little curious as to why we conspicuously left it out of mpif.h.
Bill: this is somewhat counter to the clarification you proposed.
Are you ok with this? I think the text in the standard supports what Rolf proposes.
On Jul 10, 2020, at 12:11 PM, Jeff Squyres (jsquyres) via mpiwg-fortran < [ mailto:[email protected] | [email protected] ]
wrote:
On Jul 10, 2020, at 11:18 AM, Bill Long < [ mailto:[email protected] | [email protected] ] > wrote:
In the “change” section there is this txt:
• Within the mpi_08 Fortran module, the status was defined as TYPE(MPI_Status). Additionally, within both the mpi and the mpi_f08 modules, the constants MPI_STATUS_SIZE, MPI_SOURCE, MPI_TAG, MPI_ERROR, and TYPE(MPI_Status) are defined. New conversion routines were added: MPI_STATUS_F2F08, MPI_STATUS_F082F, MPI_Status_c2f08, and MPI_Status_f082c, In mpi.h, the new type MPI_F08_status, and the external variables MPI_F08_STATUS_IGNORE and MPI_F08_STATUSES_IGNORE were added.
Good point.
Just to be clear, you're referring to the changelog section in MPI-3.1, specifically bullet 30 on p802.
That being said:
- the changelog is non-binding ...but it does indicate our intent from that time - the changelog text states that the mpi module has TYPE(MPI_Status) -- but it does not say it was added to mpif.h
1) Why would the F08 status be defined different from the C definition? (If that were the case, conversions between f08 and C would be irrelevant).
I remember that there was a lot of discussion about this at the time, which is what resulted in Figure 17.1.
I know there were discussions about making the F08 and C statuses the same, but for some reason we chose not to mandate it. Perhaps we wanted to allow implementations to do whatever they wanted...? (e.g., allow Status_c2f08 be a no-op if the implementation wanted to, but not mandate it)
2) \begin{unpopular} Why are the legacy mpi module and mpif.h still included in the spec? These are embarrassingly obsolete. If this was fixed, none of the above mentioned conversion routines would be needed. \end(unpopular}
I would love it if we could ditch -- at a minimum -- mpif.h.
However, there's oodles of legacy code out there that uses it. That's why even deprecating it gets shouted down at Forum meetings.
-- Jeff Squyres [ mailto:[email protected] | [email protected] ]
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