[mpich-discuss] On gethostbyname() and related issues on Macs

[Pavan Balaji]

On 03/01/2011 03:31 AM, Nicolas Rosner wrote:
>> I'm surprised with the error message above. Hydra should be hardcoding the
>> hostname as "localhost" in this case (see ui/mpich/mpiexec.c:277). I'm not
>> sure where the "fiona" hostname is coming from.
>
> I had told Hydra about `fiona' myself in this case (!).
>
> What I tried to say up there ("it suffices...") was: "Here's what
> happens when you DO tell Hydra explicitly about a hostname that isn't
> valid, via -hosts, -f, etc."
>
> In other words:
>
> * I found it easy to reproduce Alex's exact error messages by lying to
> Hydra directly (i.e. by explicitly requesting a host that I knew it
> wouldn't be able to resolve).
>
>      [Details: tried -hosts and -f with identical results, and IIRC,
> there was also a way to specify a machine file through an env variable
> as well (was just wondering whether Alex might have done something
> like that at some point; the cmdline options seem unlikely, since he
> said he was using exactly "mpiexec -n 2 ./a.out", right?).]

I see. I understand now.

> * However, despite many tries, I failed to run into any problem
> *without* resorting to such a direct lie (that is, merely by altering
> system settings, TCP/IP config, etc, in every odd-yet-plausible way I
> could imagine).
>
>      [Details: the goal was to hit some context (possibly a rather
> broken, yet not totally useless one, e.g. web browsing must still be
> possible) under which Hydra would choke on "mpiexec -n 2 ./a.out"
> given no further info. But it ran just fine every time, and at least
> according to the cpi example's output, never even resorted to using
> `localhost', or so it seemed.]

Got it. I'm going to punt on this bug as I have no reason to believe 
there is something wrong in the current code with Hydra.

Alex: if you are still having problems with Hydra, please speak up.

  -- Pavan

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