[mpich-discuss] PMI documentation

[Pavan Balaji]

Hi Ashley,

There are two parts to PMI -- one is the PMI interface itself, and the 
other is the wire protocol to talk to the process manager. PMI-1 (the 
first generation, which is the default now) has a bunch of interface 
functions. There isn't a good up-to-date document for this, 
unfortunately, but it's simple enough that you can just look at the 
header file in src/include/pmi.h for most of the information (there's 
good documentation in there). PMI-1 does not standardize the wire 
protocol, so there are different implementations for it including the 
default simple PMI protocol, smpd PMI protocol and slurm PMI protocol. 
You can find some more information on this here: 
http://wiki.mcs.anl.gov/mpich2/index.php/Frequently_Asked_Questions#Q:_All_my_processes_get_rank_0.

I also want to point out that our current effort is on PMI-2 (the second 
generation of the PMI interface). This is still being formulated, so 
things might (and will likely) change based on feedback on various 
folks. You can find more information on PMI2 on the below links:

http://wiki.mcs.anl.gov/mpich2/index.php/PMI_v2_Design_Thoughts
http://wiki.mcs.anl.gov/mpich2/index.php/PMI_v2_API
http://wiki.mcs.anl.gov/mpich2/index.php/PMI_v2_Wire_Protocol

  -- Pavan

On 08/27/2009 09:15 AM, Ashley Pittman wrote:
> On Wed, 2009-08-26 at 16:57 +0100, Ashley Pittman wrote:
>> Is the PMI interface documented anywhere?  I'm trying to write a new
>> client but other than the source code there doesn't seem to be any
>> documentation I can find.
> 
> I managed to get what I needed by reverse engineering the code, I made
> the rookie error of settings keys, calling barrier and then trying to
> read the keys which sometimes worked and sometimes failed.  Adding a
> barrier before exit fixed the problem for me.
> 
> That aside could somebody explain the difference between "put" and
> "publish_name", they both appear to do the same thing as far as I can
> see.
> 
> There appears to be part of a document describing PMI in the source tree
> however the directory contains most of the contents is missing, it looks
> like there should be a trunk/doc/pmi/pmiman directory however there
> isn't one.  I'm using SVN sources now although the same is true of the
> tarball.
> 
> Ashley,

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji