Re: [Mpiwg-large-counts] A perfect trick in C with similar API as with Fortran overloading - instead of the many new _l functions in C
+1 do not break ABI in this way. Thanks, Ken On 10/21/19 8:41 AM, Jeff Squyres (jsquyres) via mpiwg-large-counts wrote:
I agree: breaking ABI in this way is truly evil.
Specifically: compile your app with implementation version X. Then run your app with same implementation, but version Y (this is not uncommon for commercial ISV MPI apps). Things fail in weird, non-obvious ways (or worse, they *don't* fail, but silently give you wrong results).
Speaking as someone who writes code for a living, changing the signature of an existing, well-established function is evil. Changing it in ways that a compiler may not even warn you about (in forward- and backward-compatility scenarios) is TRULY evil.
On Oct 21, 2019, at 9:35 AM, Jeff Hammond via mpiwg-large-counts <[email protected]> wrote:
ABI is very much a user problem. We are not breaking ABI for this.
What is being done now is five years in the making. I’m not sure why you didn’t comment until recently.
Jeff
Sent from my iPhone
On Oct 20, 2019, at 10:49 PM, Rolf Rabenseifner via mpiwg-large-counts <[email protected]> wrote:
Dear Tony and all,
the group has labored over each area... 1 sided has had the least attention so far... All of MPI is to be made 64 bit clean not parts.
My proposal ia for whole MPI. Only for few routines we need some additional _x versions.
Partial answer to your earliest question in the note: Changing the meaning of existing APIs was disallowed some time ago. Certainly, for in arguments of count , replacing int with MPI_Count is a partial solution. But it changes the APIs ...
The goal is backward compatibility. And this one is provided.
In C, a program written for the assumption of big count and compiled accidentally with an MPI-3 compliant MPI will silently build and fail at runtime ... rounding of integers ...
Let's recommend to the users of the long coutnt feature that they should at a check of the version. In C, in can be tested at compile time with cpp.
and changing the AbI violates the ABI for tools and such — two possible reasons why not chosen ... but we will have to go refresh on all the reasons .
Not a user problem ...
I am sure you will get extensive feedback on these questions from the whole group ? :-)
And also by the plenum.
Best regards Rolf
----- Tony Skjellum <[email protected]> wrote:
Rolf, the group has labored over each area... 1 sided has had the least attention so far... All of MPI is to be made 64 bit clean not parts.
Partial answer to your earliest question in the note: Changing the meaning of existing APIs was disallowed some time ago. Certainly, for in arguments of count , replacing int with MPI_Count is a partial solution. But it changes the APIs ...
In C, a program written for the assumption of big count and compiled accidentally with an MPI-3 compliant MPI will silently build and fail at runtime ... rounding of integers ... and changing the AbI violates the ABI for tools and such — two possible reasons why not chosen ... but we will have to go refresh on all the reasons .
I am sure you will get extensive feedback on these questions from the whole group ? :-)
Tony
Anthony Skjellum, PhD 205-807-4968
On Oct 20, 2019, at 2:25 PM, Rolf Rabenseifner via mpiwg-large-counts <[email protected]> wrote:
Dear all,
a participant in my latest course asked me, whether we not substituting in by MPI_Count in all "int xxxxx" input arguments. The compiler automatically would cast to MPI_Count which may be a fast instruction. Then we need the new _x or _l functions only for those rare functions with MPI_Count as output or array argument.
Was this ever discussed?
Second question: Does the large Count roup plan, only to use MPI_Count for data, i.e., only in communication, I/O, and derived type routines?
Is it correct, that we keep the number of - request handles in request arrays, - ranks an size in/of communicator and group handles, will stay int?
How do we handle disp in 1-sided communication?
With this approach, it seems that explicit MPI_Count versions of a subroutine is needed only for MPI_[I][NEIGHBOR_]{ALLTOALL|ALLGATHER}{V|W} MPI_[I]{GATHER|SCATTER}V MPI_[I]REDUCE_SCATTER (18 routines) MPI_WIN_SHARED_QUERY --> *disp (1 Routine) MPI_[UN]PACK MPI_PACK_SIZE _x/_l version should have MPI_Aint (same as for MPI_...PACK..._external) (3 routines) MPI_GET_COUNT MPI_GET_ELEMENTS (has already an _X version) MPI_TYPE_SIZE (has already an _X version)
Which solution exists for MPI_CONVERSION_FN_NULL?
All other 100 routines with "int count" and "int size" seems to be solved with directly changing it into "MPI_Count count" and "MPI_Count size".
Best regards Rolf
----- Original Message -----
From: "mpiwg-large-counts" <[email protected]> To: "mpiwg-large-counts" <[email protected]> Cc: "Jeff Squyres" <[email protected]> Sent: Saturday, October 19, 2019 10:26:23 PM Subject: [Mpiwg-large-counts] Pythonizing instructions
As discussed in our last meeting, I've written a first take at instructions for Chapter Authors for how to write Pythonized functions.
These instructions are not yet intended for a wide audience -- they are intended solely for the working group. Let's iterate on them here in the WG and get them to a good enough state before sharing them widely:
https://github.com/mpiwg-large-count/large-count-issues/wiki/pythonizing
Puri/Tony/Dan: please try to use these instructions to Pythonize a few bindings. The PR for the Pythonization is https://github.com/mpiwg-large-count/mpi-standard/pull/2. All even-numbered chapters are done, and a small number of odd-numbered chapters. Grep for `funcdef` in chapter *.tex files to find a chapter that hasn't been Pythonized yet (funcdef is the LaTeX macro for hard-coded LaTeX macros).
Send your feedback here and/or we'll discuss on Wednesday.
-- Jeff Squyres [email protected]
_______________________________________________ mpiwg-large-counts mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
-- 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: Room 1.307) . _______________________________________________ mpiwg-large-counts mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
-- 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: Room 1.307) . _______________________________________________ mpiwg-large-counts mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
mpiwg-large-counts mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-large-counts
participants (1)
-
Raffenetti, Kenneth J.