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Subject: Re: [OMPI devel] orte_default_hostfile
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-12-15 12:44:26

Well, it turns out that I won't be able to do this after all. :-/

The problem is that the new hostfile handling system gets a tad upset
if it thinks a hostfile has been specified, but then it doesn't find
anything in it. I started trying to patch it to allow for the default
hostfile name to be a special case, but it winds up requiring patches
in a number of places - gets really ugly.

So I'm afraid the bottom line is that someone is going to have to
enter the name of the default hostfile if they really have one they
want us to use. Or put it in their environment.

I imagine you could do something in your code to check and set the MCA
param yourself if you want. Not sure if it's more trouble than it's
worth - have to leave that one to you.


On Dec 15, 2008, at 10:05 AM, Ralph Castain wrote:

> <laugh> can't argue with that logic! I'll make the change and file
> the CMR.
> Thanks
> Ralph
> On Dec 15, 2008, at 9:06 AM, Greg Watson wrote:
>> 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).
>> Greg
>> 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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