[Myrinet] Re: [Myricom help #13209] mapping on nt

Hi, Gabor,

On Wednesday 25 September 2002 11:41 am, Gabor Forgacs wrote:

> I have  some problem with mapping on w2k.How many host the mapper service
> should be setup ?
> I tried on all hosts / only on one host /on none of the hosts, but i always
> had some strange issues.
> Sometimes i have hosts with different maps and i just don't know why.I have
> about 5-6 hosts.

You should choose one node to be your "mapper node" and only use
that one node to map the Myrinet network.  Any re-mapping 
should be done from that same node.

If you start a mapper on several nodes at the same time, it will
cause a lot of confusion.  You'll see error messages about ID
conflicts, and you will need to remove all of the mapper 
generated files before you can start the mapper again.

And the mapper cannot be run if any GM ports are open.  You
would see error messages about that too.  So
if you've started up IP over Myrinet (ethernet emulation)
you will need to shut that down before you can run the mapper.
Or if there are any applications currently running they will
need to be killed before you can run the mapper.

Just do a gm_board_info to see if GM thinks any ports are
in use.

Here's a small description of how the mapper works.  Let's say that:

The mapper is run on node A, finds everyone, and assigns GM IDs to 
everyone. The mapper is stopped, and then you start the mapper from 
another node (B), and that mapper discovers everyone, maybe new nodes,
and will assign GM IDs. Since the mapper is run from another node, it
won't follow the same GM ID attribution pattern, so it will have to
change some GM IDs of some nodes. And if a node that it has to change
has a port open (probably IP over Myrinet, or if you mistakenly had
another mapper running on a different node), the GM ID won't be 
changed because the application may be using the previous GM ID. And
thus you will see the "id conflict" message or "ports busy" message.

Hope this helps.

Susan

-- 

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Susan Blackford
Member of Technical Staff
Myricom Inc.
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