An arbitrary number of aliases is useful in a number of ways.

For example you mention wanting to register an OPAL MCA parameter and later alias it as an OMPI MCA parameter. What if we also wanted to alias it as an ORTE level parameter. The best example I can think of is the TCP include/exclude interface MCA paramters. OPAL may need to know them for the 'if' functionality, ORTE for the OOB/tcp component, and OMPI for the BTL/tcp component. Another example might be the TMP_DIR MCA parameter discussion that has been going on in another thread. Why not have an OPAL/ORTE/OMPI variant of this parameter?

Another reason for multiple aliases is general code development. Going forward we may want to re-alias an already aliased MCA parameter to give it a 'better' name.

-- Josh


On Apr 2, 2008, at 10:50 AM, Sharon Melamed wrote:



-----Original Message-----
From: devel-core-boun...@open-mpi.org
[mailto:devel-core-boun...@open-mpi.org] On Behalf Of Jeff Squyres
Sent: Wednesday, April 02, 2008 3:44 PM
To: Open MPI Core Developers
Subject: Re: [devel-core] [RFC] Add an alias name to MCA parameter

BTW, these mails can go across devel.

devel-core is only for "private" stuff, like dialup phone numbers, etc.



On Apr 2, 2008, at 9:34 AM, Jeff Squyres wrote:
I agree that it would be beneficial to support an arbitrary number of
aliases.

Also, some points about ompi_info:

- say you register "opal_paffinity_base_alone", and later register
"mpi_paffinity_alone" as an alias.  When you "ompi_info --param mpi
all", the alias should still show up

- aliases that are displayed through ompi_info's --param option should
somehow indicate that they are aliases, and show the "real" name as
well.  Perhaps something like this?  (just an idea)

                MCA btl: parameter "mpi_paffinity_alone" (current
value: 1,
                         alias for: opal_paffinity_base_alone)
                         If nonzero, assume that this job is the
only (set of)
                         process(es) running on each node and bind
processes to
                         processors, starting with processor ID 0


On Apr 2, 2008, at 8:37 AM, Josh Hursey wrote:
This sounds great. I have a couple questions though:
- Is there a patch for this that we can look at/test?
- Do you require that the parameter be registered before adding an
alias?
- Is the 'index' argument referencing the original MCA parameter, or
are aliases given individual 'index' values?
- Does this support more than one alias for a single MCA parameter?
If so then there should be a way to specify that in the remove
function.

Cheers,
Josh

On Apr 2, 2008, at 9:22 AM, Sharon Melamed wrote:
WHAT: Add an alias name to MCA parameter.

WHY: There is a parameter that we need to register and use in OPAL
(before ompi_init) but historically the parameter name is
ompi_something_.... With the alias name we can register this
parameter in OPAL and call it opal_something_.... and then add an
alias name: ompi_something.. Now the user can use this parameter
with its real name or with its alias.

WHERE: in /opal/mca/base/

TIMOUT: Thursday - April, 10.

DESCRIPTION:
Add two Interfaces to the MCA system:

OPAL_DECLSPEC int mca_base_param_add_alias (int index, const char*
aliase);
OPAL_DECLSPEC int mca_base_param_remove_alias (int index);

These functions could be called any where in the code after the
registration of the MCA parameter. (mca_base_register)

This change includes:
        . Adding a member to mca_base_param_t structure.
        . Modifying the find functions
        . Modifying ompi_info.


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--
Jeff Squyres
Cisco Systems


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