Hi folks,
I am Laurent Broto, a Rich Graham postdoc. I'm currently working on
the BTL extraction with Greg Koenig and Rainer Keller.
At this time, I want to group all the *_bitmap function in only one
layer.
Now, you know who I am :)
So, just one question. I had in my mind:
- adding a max_size in the opal_bitmap_t structure,
- at the init time, set this field with INT_MAX or whatever the
type
is _MAX,
- add a set_max_size functions to change the max_size,
- for each function needs this test, just do if( new_size <
param->max_size) ...
I guess it is more efficient than the Jeff approach who is
supposed to
- first test if the max size has been set,
- then ensure that the bitmap never grows beyond that size.
In the first approach we only do one test, in the second one,
always
one and sometimes two.
But may I miss something...
What do you think about this ?
--
Laurent
-----Original Message-----
From: devel-boun...@open-mpi.org on behalf of Jeff Squyres
Sent: Sun 2/1/2009 7:37 AM
To: Open MPI Developers
Subject: Re: [OMPI devel] RFC: Move of ompi_bitmap_t
I just looked through both opal_bitmap_t and ompi_bitmap_t and I
think
that the only real difference is that in the ompi version, we check
(in various places) that the size of the bitmap never grows beyond
OMPI_FORTRAN_HANDLE_MAX; the opal version doesn't do these kind of
size checks.
I think it would be fairly straightforward to:
- add generic checks into the opal version, perhaps by adding a new
API call (opal_bitmap_set_max_size())
- if the max size has been set, then ensure that the bitmap never
grows beyond that size, otherwise let it have the same behavior as
today (grow without bound -- assumedly until malloc() fails)
It'll take a little care to ensure to merge the functionality
correctly, but it is possible. Once that is done, you can:
- remove the ompi_bitmap_t class
- s/ompi_bitmap/opal_bitmap/g in the OMPI layer
- add new calls to opal_bitmap_set_max_size(&bitmap,
OMPI_FORTRAN_HANDLE_MAX) in the OMPI layer (should only be in a few
places -- probably one for each MPI handle type...? It's been so
long
since I've looked at that code that I don't remember offhand)
I'd generally be in favor of this because, although this is not a
lot
of repeated code, it *is* repeated code -- so cleaning it up and
consolidating the non-Fortran stuff down in opal is not a Bad
Thing.
On Jan 30, 2009, at 4:59 PM, Ralph Castain wrote:
The history is simple. Originally, there was one bitmap_t in orte
that was also used in ompi. Then the folks working on Fortran
found
that they had to put a limit in the bitmap code to avoid getting
values outside of Fortran's range. However, this introduced a
problem - if we had the limit in the orte version, then we limited
ourselves unnecessarily, and introduced some abstraction questions
since orte knows nothing about Fortran.
So two were created. Then the orte_bitmap_t was blown away at a
later time when we removed the GPR as George felt it wasn't
necessary (which was true). It was later reborn when we needed
it in
the routed system, but this time it was done in opal as others
indicated a potential more general use for that capability.
The problem with uniting the two is that you either have to
introduce Fortran-based limits into opal (which messes up the non-
ompi uses), or deal with the Fortran limits in some other fashion.
Neither is particularly pleasant, though it could be done.
I think it primarily is a question for the Fortran folks to
address
- can they deal with Fortran limits in some other manner without
making the code unmanageable and/or taking a performance hit?
Ralph
On Jan 30, 2009, at 2:40 PM, Richard Graham wrote:
This should really be viewed as a code maintenance RFC. The
reason
this
came up in the first place is because we are investigating the
btl
move, but
these are really two very distinct issues. There are two bits of
code that
have virtually the same functionality - they do have the same
interface I am
told. The question is, is there a good reason to keep two
different
versions in the repository ? Not knowing the history of why a
second
version was created this is an inquiry. Is there some
performance
advantage, or some other advantage to having these two versions ?
Rich
On 1/30/09 3:23 PM, "Terry D. Dontje" <terry.don...@sun.com>
wrote:
I second Brian's concern. So unless this is just an
announcement
that
this is being done on a tmp branch only until everything is in
order I
think we need further discussions.
--td
Brian Barrett wrote:
So once again, I bring up my objection of this entire line of
moving
until such time as the entire process is properly mapped
out. I
believe it's premature to being moving around code in
preparation
for
a move that hasn't been proven viable yet. Until there is
concrete
evidence that such a move is possible, won't degrade
application
performance, and does not make the code totally
unmaintainable, I
believe that any related code changes should not be brought
into
the
trunk.
Brian
On Jan 30, 2009, at 12:30 PM, Rainer Keller wrote:
On behalf of Laurent Broto
RFC: Move of ompi_bitmap_t
WHAT: Move ompi_bitmap_t into opal or onet-layer
WHY: Remove dependency on ompi-layer.
WHERE: ompi/class
WHEN: Open MPI-1.4
TIMEOUT: February 3, 2009.
-------------------------------------
Details:
WHY:
The ompi_bitmap_t is being used in various places within
opal/orte/ompi. With
the proposed splitting of BTLs into a separate library, we are
currently
investigating several of the differences between ompi/class/
* and
opal/class/*
One of the items is the ompi_bitmap_t which is quite similar
to
the
opal_bitmap_t.
The question is, whether we can remove favoring a solution
just
in opal.
WHAT:
The data structures in the opal-version are the same,
so is the interface,
the implementation is *almost* the same....
The difference is the Fortran handles ;-]!
Maybe we're missing something but could we have a
discussion, on
why
Fortran
sizes are playing a role here, and if this is a hard
requirement, how
we could
settle that into that current interface (possibly without a
notion of
Fortran,
but rather, set some upper limit that the bitmap may grow to?)
With best regards,
Laurent and Rainer
--
------------------------------------------------------------------------
Rainer Keller, PhD Tel: (865) 241-6293
Oak Ridge National Lab Fax: (865) 241-4811
PO Box 2008 MS 6164 Email: kel...@ornl.gov
Oak Ridge, TN 37831-2008 AIM/Skype: rusraink
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--
Jeff Squyres
Cisco Systems
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