Sorry for the delay in response,
I totally agree with Ralph that it's not as easy as it seems,
1. rankfile mapper uses already allocated machines ( by scheduler or
hostfile ), by using rankfile as a hostfile we can run into problem
where trying to use unallocated nodes, what can hang the run.
2. we can't define in rankfile number of slots on each machine, which
means oversubscribing can take place without any warning.
3. I personally dont see any problem using hostfile, even if it has
redundant info, hostfile and rankfile belong to different layers in
the system and solve different problems. The original hostfile ( if I
recall correctly ) could bind rank to the node, but the syntax wasn't
very flexible and clear.
Lenny.
On Sun, Jun 21, 2009 at 5:15 PM, Ralph Castain <r...@open-mpi.org
<mailto:r...@open-mpi.org>> wrote:
Let me suggest a two-step process, then:
1. let's change the error message as this is easily done and thus
can be done now
2. I can look at how to eat the rankfile as a hostfile. This may
not even be possible - the problem is that the entire system is
predicated on certain ordering due to our framework architecture.
So we get an allocation, and then do a mapping against that
allocation, filtering the allocation through hostfiles, -host,
and other options.
By the time we reach the rankfile mapper, we have already
determined that we don't have an allocation and have to abort. It
is the rankfile mapper itself that looks for the -rankfile
option, so the system can have no knowledge that someone has
specified that option before that point - and thus, even if I
could parse the rankfile, I don't know it was given!
What will take time is to figure out a way to either:
(a) allow us to run the mapper even though we don't have any
nodes we know about, and allow the mapper to insert the nodes
itself - without causing non-rankfile uses to break (which could
be a major feat); or
(b) have the overall system check for the rankfile option and
pass it as a hostfile as well, assuming that a hostfile wasn't
also given, no RM-based allocation exists, etc. - which breaks
our abstraction rules and also opens a possible can of worms.
Either way, I also then have to teach the hostfile parser how to
realize it is a rankfile format and convert the info in it into
what we expected to receive from a hostfile - another non-trivial
problem.
I'm willing to give it a try - just trying to make clear why my
response was negative. It isn't as simple as it sounds...which is
why Len and I didn't pursue it when this was originally developed.
Ralph
On Sun, Jun 21, 2009 at 5:28 AM, Terry Dontje
<terry.don...@sun.com <mailto:terry.don...@sun.com>> wrote:
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....@sun.com <mailto:eugene....@sun.com>
<mailto:eugene....@sun.com <mailto:eugene....@sun.com>>>
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....@sun.com <mailto:eugene....@sun.com>
<mailto:eugene....@sun.com
<mailto:eugene....@sun.com>>> 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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