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Beginning in March 1995, the MPI Forum began meeting to
consider corrections and extensions to the original MPI Standard
document [21]. The first product of these deliberations was
Version 1.1 of the MPI specification, released in June of 1995
[22]
(see
http://www.mpi-forum.org for official MPI document releases).
At that time, effort focused
in
five areas.
1. Further corrections and clarifications for the MPI-1.1 document.
2. Additions to MPI-1.1 that do not significantly change its types of
functionality (new datatype constructors, language interoperability, etc.).
3. Completely new types of functionality (dynamic processes, one-sided
communication, parallel I/O, etc.) that are what everyone thinks of as
`` MPI-2 functionality.''
4. Bindings for Fortran 90 and C++.
MPI-2 specifies
C++ bindings
for both MPI-1 and MPI-2 functions, and extensions to the Fortran 77
binding of MPI-1 and MPI-2 to handle Fortran 90 issues.
5. Discussions of areas in which the MPI process and framework seem likely
to be useful, but where more discussion and experience are needed before
standardization (e.g.
zero-copy
semantics on shared-memory machines, real-time
specifications).
Corrections and clarifications (items of type 1 in the above list)
were
collected in Chapter 3 of the MPI-2 document:
``Version 1.2 of MPI.''
That
chapter also contains the function for
identifying the version number. Additions to MPI-1.1 (items of
types 2, 3, and 4 in the above list) are in the
remaining chapters of the MPI-2 document,
and constitute the specification for
MPI-2.
Items of type 5 in the
above list have been moved to a separate document, the `` MPI Journal
of Development'' (JOD), and are not part of the MPI-2 Standard.
This structure makes it easy for users and implementors to understand
what level of MPI compliance a given implementation has:
- MPI-1 compliance will mean compliance with
MPI-1.3.
This is a useful level of compliance. It means that the
implementation conforms to the clarifications of MPI-1.1 function
behavior given in Chapter 3 of the MPI-2 document. Some
implementations may require changes to be MPI-1 compliant.
- MPI-2 compliance will mean compliance with all of
MPI-2.1.
- The MPI Journal of Development is not part of the MPI Standard.
It is to be emphasized that forward compatibility is preserved. That is,
a valid MPI-1.1 program is both a valid
MPI-1.3
program and a valid
MPI-2.1
program, and a valid
MPI-1.3
program is a valid
MPI-2.1
program.
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