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Subject: Re: [OMPI devel] orte_default_hostfile
From: Greg Watson (g.watson_at_[hidden])
Date: 2008-12-15 11:06:45

Hi Ralph,

I think mainly because it simplifies installation of ompi for PTP
users. Since PTP uses the hostfile to display the system
configuration, we're pretty much always going to have one (although
PTP does work without it, feedback is more limited). It's much easier
for people to add a list of hosts to a file, than have to go and add
something to the param file as well (it's hard enough to get them to
do the former correctly).


On Dec 15, 2008, at 1:51 PM, Ralph Castain wrote:

> Can you help me understand something here? I'm not opposed to making
> the change - just puzzled as to why the value of the default
> hostfile name is of concern to Eclipse.
> There is one reason not to set a default name - it causes us to open
> and read that file, even though nobody ever put something in it.
> Remember, we distribute and install an empty default hostfile that
> contains instructions on how to build one, so it will always exist.
> Since the name of the default hostfile can be set in the default MCA
> param file, environment, or cmd line, there didn't seem to be any
> real reason to define some special name.
> It isn't a big deal, though, so I don't really care that much. But I
> would like to understand why Eclipse cares so we can factor that
> into any future thinking.
> Ralph
> On Dec 12, 2008, at 7:11 AM, Greg Watson wrote:
>> From our perspective, it would be good if it could default to the
>> old behavior (in 1.3 if possible).
>> Thanks,
>> Greg
>> On Dec 8, 2008, at 11:42 AM, Ralph Castain wrote:
>>> I don't think there was any overt thought given to it, at least
>>> not on my part. I suspect it came about because (a) the wiki
>>> defining hostfile behavior made no mention of the default value,
>>> (b) I may have overlooked the prior default when rewriting that
>>> code, and (c) since we now have default-hostfile as well as
>>> hostfile, it could be I didn't default the name since it isn't
>>> clear which one should get the default.
>>> I honestly don't remember - this has been in the code base for a
>>> really long time now.
>>> I have no iron in this fire - as you know, all of our environs
>>> here are managed. So I guess I'll throw it out there to the
>>> community:
>>> do we want --default-hostfile to have a default value?
>>> Pros: it could be considered a continuation of 1.2's hostfile
>>> behavior
>>> Cons: we treat hostfile in a totally different way in 1.3. We now
>>> have two hostfiles: a default that applies to all app_contexts,
>>> and a hostfile that applies to only one app_context. It would seem
>>> that the default-hostfile best aligns with the old "hostfile"
>>> behavior, but could lead to some confusion in its new usage.
>>> Any preferences/thoughts?
>>> Ralph
>>> On Dec 5, 2008, at 9:15 AM, Greg Watson wrote:
>>>> Hi,
>>>> In 1.2.x, the rds_hostfile_path parameter pointed to openmpi-
>>>> default-hostfile by default. This parameter has been replaced
>>>> with orte_default_hostfile in 1.3, but now it defaults to <none>.
>>>> Was there any particular reason for the default value to change?
>>>> Greg
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