-
Opens
- Alexander is not going to be in Menlo Park, will
work with Rich to find an
adequate solution
- Subsetting: way
forward
- Subsetting in its extreme form (all of the
standard is composed of subsets that have user defined hierarchies, attach to
opaque objects, etc.) does not seem to be terribly practicable. However,
architectural influence, performance, and memory footprint aspects of subsetting
warrant further research and discussion in this
area.
- During the discussion so far we've
considered several proposals that apparently go in the subsetting
direction, or at least overlap in some parts with the subsetting idea, in
that they allow control of the essential aspects related to performance and
memory footprint. The WG feels compelled to express their opinion about some of
these ideas as follows:
- Runtime
- The subsetting WG supports Dick
Treumann's MPI_Init time int based assertion proposal as expressed in a series
of emails, and encourages creation of a full proposal, with the following
notes:
- The set of standard
assertions should be settled and accepted by all
implementors
- The question of allowing
or disallowing implementation specific assertions should be
resolved
- The distinction between
assertions and hints should be formulated in a way understandable to a first
time user
- The matter of underlying
libraries and tools in their relation to assertions should be
clarified
- It looks that
tools that intercept the MPI_Init_* call family will be able to deal with
assertions they cannot support by basically ignoring
them
- Layered
underlying libraries are unlikely to be allowed to change assertions already in
effect, or adding their own assertions on top of them. These libraries should
either adapt themselves to the defined assertions, or bail
out
- The subsetting WG would like to see
more details of Jeff Squyres' proposal on Info based data passing in and out of
MPI library before it expresses its opinion, with the following
notes:
- The effect of setting
certain internal thresholds, like eager threshold, should be considered as a
collective action on all processes
- Generally, the WG does not see a compelling need for
assertions/hints/subsets to be attached to the communicator/window/file or other
MPI entities, as this does not seem to be directly usable for performance
increase or memory footprint
reduction
- Link time
- The WG does not see the need to either
specify or prohibit specific link time arrangements like various library names,
versions, combinations, dynamic loading thereof, etc. The details should be left
to the implementation, with the ABI and compatibility aspects in
mind.
- Compile
time
- The WG encourages Reiner Keller to
produce a full proposal, minding the ABI and application/MPI compatibility
aspects
- Actions
- Please provide feedback to these minutes by end of
week
- Alexander will change the proposal in the Wiki
accordingly by the time of the MPI Forum
meeting