Floating-point CAS is valid as a way to implement "if this hasn't changed, put the results of this operation in place". It gives you a (moderately expensive, not very fair) way to build a form of arbitrary atomics. Keith
-----Original Message----- From: [email protected] [mailto:mpi3-rma- [email protected]] On Behalf Of Jeff Hammond Sent: Tuesday, July 17, 2012 7:26 PM To: MPI 3.0 Remote Memory Access working group Subject: Re: [Mpi3-rma] notes from 5pm Tuesday meeting @ July 2012 Forum
I don't know that floating-point compare is well-defined. You really have ask "if abs(x-y)<tolerance" and not "if x==y".
I think only fixed-point types should be valid for CAS.
Jeff
On Tue, Jul 17, 2012 at 6:14 PM, Dave Goodell <[email protected]> wrote:
Discussed the complex types in COMPARE_AND_SWAP issue. "Fortran Integer" category is permitted, but "Complex" category is not, primarily because of width. Since "Fortran Integer" contains wide types, shouldn't we just permit "Complex" and "Floating point" as well? Consensus was to stick with the existing text which permits only "C integer, Fortran integer, Logical, Multi-language types, or Byte".
Group review (esp. Jim & Sreeram): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/187
incorporate Jim suggested change (Torsten): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/271
we think we are unaffected, but need a second check (Jim): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/278
Double-check that C++ is not referenced in the RMA chapter (Pavan): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/281
Needs review (Dave): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/300
Think unaffected, but slim chance of Rput/Rget being affected (Pavan): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/317
Need to check implementation of various (4?) "flush is non-local" changes (Dave): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/270
Need to check disp_unit change (Jim & Sreeram): https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/284
After the above items have all been dealt with, all chapter committee members should re-read the whole chapter in the *clean* document (the one _without_ the changebars and colored text) to look for obvious typos and inconsistencies.
-Dave
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-- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
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