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Subject: Re: [OMPI devel] why does --rankfile need hostlist?
From: Terry Dontje (Terry.Dontje_at_[hidden])
Date: 2009-06-21 07:28:39


Being a part of these discussions I can understand your reticence to
reopen this discussion. However, I think this is a major usability
issue with this feature which actually is fairly important in order to
get things to run performant. Which IMO is important.

That being said I think there are one of two things that could be done
to mitigate the issue.

1. To eliminate the element of surprise by changing mpirun to eat
rankfile without the hostfile.
2. To change the error message to something understandable by the user
such that they
know they might be missing the hostfile option.

Again I understand this topic is frustrating and there are some
boundaries with the design that make these two option orthogonal to each
other but I really believe we need to make the rankfile option something
that is easily usable by our users.

--td

Ralph Castain wrote:
> Having gone around in circles on hostfile-related issues for over five
> years now, I honestly have little motivation to re-open the entire
> discussion again. It doesn't seem to be that daunting a requirement
> for those who are using it, so I'm inclined to just leave well enough
> alone.
>
> :-)
>
>
> On Fri, Jun 19, 2009 at 2:21 PM, Eugene Loh <Eugene.Loh_at_[hidden]
> <mailto:Eugene.Loh_at_[hidden]>> wrote:
>
> Ralph Castain wrote:
>> The two files have a slightly different format
> Agreed.
>> and completely different meaning.
> Somewhat agreed. They're both related to mapping processes onto a
> cluster.
>
>> The hostfile specifies how many slots are on a node. The rankfile
>> specifies a rank and what node/slot it is to be mapped onto.
> Agreed.
>
>> Rankfiles can use relative node indexing and refer to nodes
>> received from a resource manager - i.e., without any hostfile.
> This is the main part I'm concerned about. E.g.,
>
> % cat rankfile
> rank 0=node0 slot=0
> rank 1=node1 slot=0
> % mpirun -np 2 -rf rankfile ./a.out
> --------------------------------------------------------------------------
> Rankfile claimed host node1 that was not allocated or
> oversubscribed it's slots:
>
> --------------------------------------------------------------------------
> [node0:14611] [[61560,0],0] ORTE_ERROR_LOG: Bad parameter in file
> rmaps_rank_file.c at line 107
> [node0:14611] [[61560,0],0] ORTE_ERROR_LOG: Bad parameter in file
> base/rmaps_base_map_job.c at line 86
> [node0:14611] [[61560,0],0] ORTE_ERROR_LOG: Bad parameter in file
> base/plm_base_launch_support.c at line 86
> [node0:14611] [[61560,0],0] ORTE_ERROR_LOG: Bad parameter in file
> plm_rsh_module.c at line 1016
> % mpirun -np 2 -host node0,node1 -rf rankfile ./a.out
> 0 on node0
> 1 on node1
> done
>
> It seems to me that the rankfile has sufficient information to
> express what I want it to do. But mpirun won't accept this. To
> fix this, I have to, e.g., supply/maintain/specify redundant
> information in a hostfile or host list.
>
>> So the files are intentionally quite different. Trying to combine
>> them would be rather ugly.
> Right. And my issue is that I'm forced to use both when I only
> want rankfile functionality.
>
>> On Thu, Jun 18, 2009 at 1:52 PM, Eugene Loh <Eugene.Loh_at_[hidden]
>> <mailto:Eugene.Loh_at_[hidden]>> wrote:
>>
>> In order to use "mpirun --rankfile", I also need to specify
>> hosts/hostlist. But that information is redundant with what
>> I provide in the rankfile. So, from a user's point of view,
>> this strikes me as broken. Yes? Should I file a ticket, or
>> am I missing something here about this functionality?
>>
>
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