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openmpi/opal/mca/event/base
Nathan Hjelm cf377db823 MCA/base: Add new MCA variable system
Features:
 - Support for an override parameter file (openmpi-mca-param-override.conf).
   Variable values in this file can not be overridden by any file or environment
   value.
 - Support for boolean, unsigned, and unsigned long long variables.
 - Support for true/false values.
 - Support for enumerations on integer variables.
 - Support for MPIT scope, verbosity, and binding.
 - Support for command line source.
 - Support for setting variable source via the environment using
   OMPI_MCA_SOURCE_<var name>=source (either command or file:filename)
 - Cleaner API.
 - Support for variable groups (equivalent to MPIT categories).

Notes:
 - Variables must be created with a backing store (char **, int *, or bool *)
   that must live at least as long as the variable.
 - Creating a variable with the MCA_BASE_VAR_FLAG_SETTABLE enables the use of
   mca_base_var_set_value() to change the value.
 - String values are duplicated when the variable is registered. It is up to
   the caller to free the original value if necessary. The new value will be
   freed by the mca_base_var system and must not be freed by the user.
 - Variables with constant scope may not be settable.
 - Variable groups (and all associated variables) are deregistered when the
   component is closed or the component repository item is freed. This
   prevents a segmentation fault from accessing a variable after its component
   is unloaded.
 - After some discussion we decided we should remove the automatic registration
   of component priority variables. Few component actually made use of this
   feature.
 - The enumerator interface was updated to be general enough to handle
   future uses of the interface.
 - The code to generate ompi_info output has been moved into the MCA variable
   system. See mca_base_var_dump().

opal: update core and components to mca_base_var system
orte: update core and components to mca_base_var system
ompi: update core and components to mca_base_var system

This commit also modifies the rmaps framework. The following variables were
moved from ppr and lama: rmaps_base_pernode, rmaps_base_n_pernode,
rmaps_base_n_persocket. Both lama and ppr create synonyms for these variables.

This commit was SVN r28236.
2013-03-27 21:09:41 +00:00
..
base.h Sorry for mid-day commit, but I had promised on the call to do this upon my return. 2012-04-06 14:23:13 +00:00
event_base_close.c Per RFC modify the behavior of mca_base_components_close to NOT close the output. Modify frameworks to always close their output and set to -1. 2012-11-06 19:09:26 +00:00
event_base_open.c MCA/base: Add new MCA variable system 2013-03-27 21:09:41 +00:00
Makefile.am Update libevent to the 2.0 series, currently at 2.0.7rc. We will update to their final release when it becomes available. Currently known errors exist in unused portions of the libevent code. This revision passes the IBM test suite on a Linux machine and on a standalone Mac. 2010-10-24 18:35:54 +00:00
README.openmpi Include the libevent headers when --with-devel-headers is specified. Ensure that the proper include paths are added to the wrapper compilers - thanks to Jeff for figuring out how to do it. 2010-10-28 21:26:07 +00:00

Last updated: 15 Sep 2010

How to update the Libevent embedded in OPAL
-------------------------------------------

OPAL requires some modification of the Libevent build system in order
to properly operate. In addition, OPAL accesses the Libevent functions
through a set of wrappers - this is done for three reasons:

1. Hide the Libevent functions. Some applications directly call
   libevent APIs and expect to operate against a locally installed
   library. Since the library used by OPAL may differ in version, and
   to avoid linker errors for multiply-defined symbols, it is
   important that the libevent functions included in OPAL be "hidden"
   from external view. Thus, OPAL's internal copy of libevent is built
   with visibility set to "hidden" and all access from the OPAL code
   base is done through "opal_xxx" wrapper API calls.

   In those cases where the system is built against a compiler that
   doesn't support visibility, conflicts can (unfortunately)
   arise. However, since only a very few applications would be
   affected, and since most compilers support visibility, we do not
   worry about this possibility.

2. Correct some deficiencies in the distributed Libevent configuration
   tests.  Specifically, the distributed tests for kqueue and epoll
   support provide erroneous results on some platforms (as determined
   by our empirical testing). OPAL therefore provides enhanced tests
   to correctly assess those environments.
   
3. Enable greater flexibility in configuring Libevent for the specific
   environment. In particular, OPAL has no need of Libevent's dns,
   http, and rpc events, so configuration options to remove that code
   from Libevent have been added.

The procedure for updating Libevent has been greatly simplified
compared to prior versions in the OPAL code base by replacing
file-by-file edits with configuration logic. Thus, updating the
included libevent code can generally be accomplished by:

1. create a new opal/mca/event component for the updated version, using
   a name "libeventxxx", where xxx = libevent version. For example,
   libevent 2.0.7 => component libevent207

2. create a subdirectory "libevent" in the new component and unpack the
   new libevent code tarball into it.

3. copy the configure.m4, autogen.subdirs, component.c, moduule.c,
   Makefile.am, and .h files from a prior version to the new component.
   You will need to customize them for the new version, but they can
   serve as a good template. In many cases, you will just have to update
   the component name.

4. edit libevent/configure.in to add OMPI specific options and modes.
   Use the corresponding file from a prior version as a guide. The
   necessary changes are marked with "OMPI" comments. These changes
   have been pushed upstream to libevent, and so edits may no longer
   be required in the new version.

5. Modify libevent/Makefile.am. Here again, you should use the file from
   a prior version as an example. Hopefully, you can just use the file
   without change - otherwise, the changes will have to be done by hand.
   Required changes reflect the need for OMPI to turn "off" unused
   subsystems such as http. These changes have been pushed upstream to
   libevent, and so edits may no longer be required in the new version.

6. in your new component Makefile.am, note that the libevent headers
   are listed by name when WITH_INSTALL_HEADERS is given. This is required
   to support the OMPI --with-devel-headers configure option. Please review
   the list and update it to include all libevent headers for the new
   version.