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MPI_Alltoallw is inconsistent in its definition because it has byte displacements. #106

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tonyskjellum opened this issue Sep 19, 2018 · 4 comments
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errata Errata items for the previous MPI Standard wg-collectives Collectives Working Group wg-large-counts Large Counts Working Group

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@tonyskjellum
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Problem

MPI_Alltoallw is inconsistent in its definition because it has byte displacements.

Proposal

MPI_Alltoallw is inconsistent in its definition because it has byte displacements, yet they are defined as int, not MPI_Aint.

So, we need a ticket as an "Advice to Users" in the Collective Chapter. Notice that a solution from Big MPI Ticket #80 will address this in an _x API. But, we also want to document the limitation of the existing API, which remains in use.

Changes to the Text

An advice to users will be added beneath the MPI_Alltoallw definition.

Impact on Implementations

None.

Impact on Users

It is just a warning. It may induce users to use MPI_Neighbor_alltoallw or to use MPI_Alltoallw_x (if adopted).

References

See Ticket #80 and https://github.com/mpi-forum/mpi-standard/pull/34 .

@tonyskjellum tonyskjellum self-assigned this Sep 19, 2018
@tonyskjellum tonyskjellum added wg-large-counts Large Counts Working Group wg-collectives Collectives Working Group labels Sep 19, 2018
@tonyskjellum tonyskjellum added this to the 2018-12 San Jose, USA milestone Sep 19, 2018
@jeffhammond
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jeffhammond commented Sep 19, 2018 via email

@tonyskjellum tonyskjellum added the errata Errata items for the previous MPI Standard label Sep 24, 2018
@tonyskjellum
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Reopen?

@dholmes-epcc-ed-ac-uk
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@tonyskjellum re-visit for consideration when MPI-4k (pronounced MPI-fork) is in full swing.

@jsquyres
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Please don't use the term "fork" -- per #80 (comment).

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Labels
errata Errata items for the previous MPI Standard wg-collectives Collectives Working Group wg-large-counts Large Counts Working Group
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