Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] Unable to connect to a server using MX MTL with TCP
From: Audet, Martin (Martin.Audet_at_[hidden])
Date: 2010-06-09 19:17:28


Thanks to both Scott and Jeff !

Next time I have a problem, I will check the README file first (Doh !).

Also we might mitigate the problem by connecting the workstation to the Myrinet switch.

Martin

-----Original Message-----
From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On Behalf Of Jeff Squyres
Sent: June 9, 2010 15:34
To: Open MPI Users
Subject: Re: [OMPI users] Unable to connect to a server using MX MTL with TCP

On Jun 5, 2010, at 7:52 AM, Scott Atchley wrote:

> I do not think this is a supported scenario. George or Jeff can correct me, but when you use the MX MTL you are using the pml cm and not the pml ob1. The BTLs are part of ob1. When using the MX MTL, it cannot use the TCP BTL.
>
> You only solution would be to use the MX BTL.

Sorry for the delayed reply.

Scott is correct; the MX MTL uses the "cm" PML. The "cm" PML can only use *one* MTL at a time (little known fact of Open MPI lore: "cm" stands for several things, one of which is "Connor MacLeod" -- there can only be one).

Here's a chunk of text from the README:

- There are three MPI network models available: "ob1", "csum", and
  "cm". "ob1" and "csum" use BTL ("Byte Transfer Layer") components
  for each supported network. "cm" uses MTL ("Matching Tranport
  Layer") components for each supported network.

  - "ob1" supports a variety of networks that can be used in
    combination with each other (per OS constraints; e.g., there are
    reports that the GM and OpenFabrics kernel drivers do not operate
    well together):
    - OpenFabrics: InfiniBand and iWARP
    - Loopback (send-to-self)
    - Myrinet: GM and MX (including Open-MX)
    - Portals
    - Quadrics Elan
    - Shared memory
    - TCP
    - SCTP
    - uDAPL

  - "csum" is exactly the same as "ob1", except that it performs
    additional data integrity checks to ensure that the received data
    is intact (vs. trusting the underlying network to deliver the data
    correctly). csum supports all the same networks as ob1, but there
    is a performance penalty for the additional integrity checks.

  - "cm" supports a smaller number of networks (and they cannot be
    used together), but may provide better better overall MPI
    performance:
    - Myrinet MX (including Open-MX, but not GM)
    - InfiniPath PSM
    - Portals

  Open MPI will, by default, choose to use "cm" when the InfiniPath
  PSM MTL can be used. Otherwise, "ob1" will be used and the
  corresponding BTLs will be selected. "csum" will never be selected
  by default. Users can force the use of ob1 or cm if desired by
  setting the "pml" MCA parameter at run-time:

    shell$ mpirun --mca pml ob1 ...
    or
    shell$ mpirun --mca pml csum ...
    or
    shell$ mpirun --mca pml cm ...

-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/
_______________________________________________
users mailing list
users_at_[hidden]
http://www.open-mpi.org/mailman/listinfo.cgi/users