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From: George Bosilca (bosilca_at_[hidden])
Date: 2007-06-13 11:32:27


On Wed, 13 Jun 2007, Gleb Natapov wrote:

>> I'm not particularly fond of creating variable MCA parameters after
>> the btl open call because they won't show up in ompi_info. Should we
>> do something else if you want to override bandwidths, perhaps
>> something similar to the HCA params file? If you recall, we made the
>> HCA params stuff a file because of exactly this issue: we didn't want
>> variable MCA parameters and we didn't want to have to make the user
>> type out a potentially long set of complex MCA parameters that were
>> dependent upon the exact environment that the user was running in.
>
> I modeled this after TCP BTL so blame George :) I actually like this
> notation, but obviously it has its shortcomings. I am open to other ideas
> if they can be implemented in a short time frame.

Right ... blame me :) The problem is that we have to know the number of
interfaces in order to be able to generate the MCA parameters, and the
number of interfaces will only be know inside the init call (and I really
doon't think it's a good idea to move this part of the code in the open
function).

I don't mind having some MCA parameters that are never showed by ompi_info
(we already have the hidden ones). Anyway, for TCP by default there is the
btl_tcp_latency and btl_tcp_bandwidth which will be used as a default
value for all NICs. For the others, a quick google search on our mailing
list will return all information about how to set the latency and
bandwidth by NIC. MX have a similar mechanism ...

   Thanks,
     george.