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Subject: Re: [OMPI devel] -display-map
From: Greg Watson (g.watson_at_[hidden])
Date: 2008-12-02 16:03:54

Ralph, will this be in 1.3rc1?


On Nov 24, 2008, at 3:06 PM, Greg Watson wrote:

> Great, thanks. I'll take a look once it comes over to 1.3.
> Cheers,
> Greg
> On Nov 24, 2008, at 2:59 PM, Ralph Castain wrote:
>> Yo Greg
>> This is in the trunk as of r20032. I'll bring it over to 1.3 in a
>> few days.
>> I implemented it as another MCA param
>> "orte_show_resolved_nodenames" so you can actually get the info as
>> you execute the job, if you want. The xml tag is "noderesolve" -
>> let me know if you need any changes.
>> Ralph
>> On Oct 22, 2008, at 11:55 AM, Greg Watson wrote:
>>> Ralph,
>>> I guess the issue for us is that we will have to run two commands
>>> to get the information we need. One to get the configuration
>>> information, such as version and MCA parameters, and one to get
>>> the host information, whereas it would seem more logical that this
>>> should all be available via some kind of "configuration discovery"
>>> command. I understand the issue with supplying the hostfile
>>> though, so maybe this just points at the need for us to separate
>>> configuration information from the host information. In any case,
>>> we'll work with what you think is best.
>>> Greg
>>> On Oct 20, 2008, at 4:49 PM, Ralph Castain wrote:
>>>> Hmmm...just to be sure we are all clear on this. The reason we
>>>> proposed to use mpirun is that "hostfile" has no meaning outside
>>>> of mpirun. That's why ompi_info can't do anything in this regard.
>>>> We have no idea what hostfile the user may specify until we
>>>> actually get the mpirun cmd line. They may have specified a
>>>> default-hostfile, but they could also specify hostfiles for the
>>>> individual app_contexts. These may or may not include the node
>>>> upon which mpirun is executing.
>>>> So the only way to provide you with a separate command to get a
>>>> hostfile<->nodename mapping would require you to provide us with
>>>> the default-hostifle and/or hostfile cmd line options just as if
>>>> you were issuing the mpirun cmd. We just wouldn't launch - but it
>>>> would be the exact equivalent of doing "mpirun --do-not-launch".
>>>> Am I missing something? If so, please do correct me - I would be
>>>> happy to provide a tool if that would make it easier. Just not
>>>> sure what that tool would do.
>>>> Thanks
>>>> Ralph
>>>> On Oct 19, 2008, at 1:59 PM, Greg Watson wrote:
>>>>> Ralph,
>>>>> It seems a little strange to be using mpirun for this, but
>>>>> barring providing a separate command, or using ompi_info, I
>>>>> think this would solve our problem.
>>>>> Thanks,
>>>>> Greg
>>>>> On Oct 17, 2008, at 10:46 AM, Ralph Castain wrote:
>>>>>> Sorry for delay - had to ponder this one for awhile.
>>>>>> Jeff and I agree that adding something to ompi_info would not
>>>>>> be a good idea. Ompi_info has no knowledge or understanding of
>>>>>> hostfiles, and adding that capability to it would be a major
>>>>>> distortion of its intended use.
>>>>>> However, we think we can offer an alternative that might better
>>>>>> solve the problem. Remember, we now treat hostfiles in a very
>>>>>> different manner than before - see the wiki page for a complete
>>>>>> description, or "man orte_hosts".
>>>>>> So the problem is that, to provide you with what you want, we
>>>>>> need to "dump" the information from whatever default-hostfile
>>>>>> was provided, and, if no default-hostfile was provided, then
>>>>>> the information from each hostfile that was provided with an
>>>>>> app_context.
>>>>>> The best way we could think of to do this is to add another
>>>>>> mpirun cmd line option --dump-hostfiles that would output the
>>>>>> line-by-line name from the hostfile plus the name we resolved
>>>>>> it to. Of course, --xml would cause it to be in xml format.
>>>>>> Would that meet your needs?
>>>>>> Ralph
>>>>>> On Oct 15, 2008, at 3:12 PM, Greg Watson wrote:
>>>>>>> Hi Ralph,
>>>>>>> We've been discussing this back and forth a bit internally and
>>>>>>> don't really see an easy solution. Our problem is that Eclipse
>>>>>>> is not running on the head node, so gethostbyname will not
>>>>>>> necessarily resolve to the same address. For example, the
>>>>>>> hostfile might refer to the head node by an internal network
>>>>>>> address that is not visible to the outside world. Since
>>>>>>> gethostname also looks in /etc/hosts, it may resolve locally
>>>>>>> but not on a remote system. The only think I can think of
>>>>>>> would be, rather than us reading the hostfile directly as we
>>>>>>> do now, to provide an option to ompi_info that would dump the
>>>>>>> hostfile using the same rules that you apply when you're using
>>>>>>> the hostfile. Would that be feasible?
>>>>>>> Greg
>>>>>>> On Sep 22, 2008, at 4:25 PM, Ralph Castain wrote:
>>>>>>>> Sorry for delay - was on vacation and am now trying to work
>>>>>>>> my way back to the surface.
>>>>>>>> I'm not sure I can fix this one for two reasons:
>>>>>>>> 1. In general, OMPI doesn't really care what name is used for
>>>>>>>> the node. However, the problem is that it needs to be
>>>>>>>> consistent. In this case, ORTE has already used the name
>>>>>>>> returned by gethostname to create its session directory
>>>>>>>> structure long before mpirun reads a hostfile. This is why we
>>>>>>>> retain the value from gethostname instead of allowing it to
>>>>>>>> be overwritten by the name in whatever allocation we are
>>>>>>>> given. Using the name in hostfile would require that I either
>>>>>>>> find some way to remember any prior name, or that I tear down
>>>>>>>> and rebuild the session directory tree - neither seems
>>>>>>>> attractive nor simple (e.g., what happens when the user
>>>>>>>> provides multiple entries in the hostfile for the node, each
>>>>>>>> with a different IP address based on another interface in
>>>>>>>> that node? Sounds crazy, but we have already seen it done -
>>>>>>>> which one do I use?).
>>>>>>>> 2. We don't actually store the hostfile info anywhere - we
>>>>>>>> just use it and forget it. For us to add an XML attribute
>>>>>>>> containing any hostfile-related info would therefore require
>>>>>>>> us to re-read the hostfile. I could have it do that -only- in
>>>>>>>> the case of "XML output required", but it seems rather ugly.
>>>>>>>> An alternative might be for you to simply do a
>>>>>>>> "gethostbyname" lookup of the IP address or hostname to see
>>>>>>>> if it matches instead of just doing a strcmp. This is what we
>>>>>>>> have to do internally as we frequently have problems with
>>>>>>>> FQDN vs. non-FQDN vs. IP addresses etc. If the local OS
>>>>>>>> hasn't cached the IP address for the node in question it can
>>>>>>>> take a little time to DNS resolve it, but otherwise works fine.
>>>>>>>> I can point you to the code in OPAL that we use - I would
>>>>>>>> think something similar would be easy to implement in your
>>>>>>>> code and would readily solve the problem.
>>>>>>>> Ralph
>>>>>>>> On Sep 19, 2008, at 7:18 AM, Greg Watson wrote:
>>>>>>>>> Ralph,
>>>>>>>>> The problem we're seeing is just with the head node. If I
>>>>>>>>> specify a particular IP address for the head node in the
>>>>>>>>> hostfile, it gets changed to the FQDN when displayed in the
>>>>>>>>> map. This is a problem for us as we need to be able to match
>>>>>>>>> the two, and since we're not necessarily running on the head
>>>>>>>>> node, we can't always do the same resolution you're doing.
>>>>>>>>> Would it be possible to use the same address that is
>>>>>>>>> specified in the hostfile, or alternatively provide an XML
>>>>>>>>> attribute that contains this information?
>>>>>>>>> Thanks,
>>>>>>>>> Greg
>>>>>>>>> On Sep 11, 2008, at 9:06 AM, Ralph Castain wrote:
>>>>>>>>>> Not in that regard, depending upon what you mean by
>>>>>>>>>> "recently". The only changes I am aware of wrt nodes
>>>>>>>>>> consisted of some changes to the order in which we use the
>>>>>>>>>> nodes when specified by hostfile or -host, and a little #if
>>>>>>>>>> protectionism needed by Brian for the Cray port.
>>>>>>>>>> Are you seeing this for every node? Reason I ask: I can't
>>>>>>>>>> offhand think of anything in the code base that would
>>>>>>>>>> replace a host name with the FQDN because we don't get that
>>>>>>>>>> info for remote nodes. The only exception is the head node
>>>>>>>>>> (where mpirun sits) - in that lone case, we default to the
>>>>>>>>>> name returned to us by gethostname(). We do that because
>>>>>>>>>> the head node is frequently accessible on a more global
>>>>>>>>>> basis than the compute nodes - thus, the FQDN is required
>>>>>>>>>> to ensure that there is no address confusion on the network.
>>>>>>>>>> If the user refers to compute nodes in a hostfile or -host
>>>>>>>>>> (or in an allocation from a resource manager) by non-FQDN,
>>>>>>>>>> we just assume they know what they are doing and the name
>>>>>>>>>> will correctly resolve to a unique address.
>>>>>>>>>> On Sep 10, 2008, at 9:45 AM, Greg Watson wrote:
>>>>>>>>>>> Hi,
>>>>>>>>>>> Has there been a change in the behavior of the -display-
>>>>>>>>>>> map option has changed recently in the 1.3 branch. We're
>>>>>>>>>>> now seeing the host name as a fully resolved DN rather
>>>>>>>>>>> than the entry that was specified in the hostfile. Is
>>>>>>>>>>> there any particular reason for this? If so, would it be
>>>>>>>>>>> possible to add the hostfile entry to the output since we
>>>>>>>>>>> need to be able to match the two?
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Greg
>>>>>>>>>>> _______________________________________________
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