Re: [OMPI devel] New mapper module

[Jeff Squyres]

Sweet!

On Apr 17, 2008, at 10:06 AM, Ralph H Castain wrote:

I have implemented and committed (r18190) a new RMAPS module that
sequentially maps ranks to the hosts listed in a hostfile. You must  
set -mca
rmaps seq in order to access this module - it will -not- be selected  
any

other way.

The basic method of operation respects the hostfile descriptions on  
the wiki

page, but I will describe it here briefly as well:

1. if we are in a managed environment, we will only map to nodes  
within the
allocation. If your hostfile contains nodes outside the allocation,  
we will
report an error and abort. So if you want to map ranks sequentially,  
you
need to be sure that the hostfile describing this mapping contains  
only
hosts that -can- be mapped. In an unmanaged environment, we  
automatically

include all the nodes in any specified hostfiles, so this won't be a
problem.

2. if you specify a default-hostfile, we will use it - however, any
hostfiles specified for an app_context will override the default- 
hostfile.
Any apps that do -not- have a hostfile specified will be mapped  
sequentially

to the hosts in the default-hostfile

3. if your app_context does not specify a number of procs, we will
automatically map one proc to each and every entry in the hostfile

4. if your app_context does specify a number of procs, we will  
sequentially

map that number of procs, one to each entry in the hostfile. Multiple
app_contexts are supported, with the sequence continuing across the
app_contexts.

5. if you specify a number of procs greater than the number of  
entries in
your hostfile, we will map the overrun using byslot rules - i.e., we  
will
start by filling the remaining slots on the first node in your  
hostfile,

then proceed to fill the second node in your hostfile, etc.

6. if your allocation does not permit oversubscription, we will  
report an
error and abort if you attempt to place more procs on a node than  
slots.


Hope that helps
Ralph


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--
Jeff Squyres
Cisco Systems

[OMPI devel] New mapper module

[Ralph H Castain]

I have implemented and committed (r18190) a new RMAPS module that
sequentially maps ranks to the hosts listed in a hostfile. You must set -mca
rmaps seq in order to access this module - it will -not- be selected any
other way.

The basic method of operation respects the hostfile descriptions on the wiki
page, but I will describe it here briefly as well:

1. if we are in a managed environment, we will only map to nodes within the
allocation. If your hostfile contains nodes outside the allocation, we will
report an error and abort. So if you want to map ranks sequentially, you
need to be sure that the hostfile describing this mapping contains only
hosts that -can- be mapped. In an unmanaged environment, we automatically
include all the nodes in any specified hostfiles, so this won't be a
problem.

2. if you specify a default-hostfile, we will use it - however, any
hostfiles specified for an app_context will override the default-hostfile.
Any apps that do -not- have a hostfile specified will be mapped sequentially
to the hosts in the default-hostfile

3. if your app_context does not specify a number of procs, we will
automatically map one proc to each and every entry in the hostfile

4. if your app_context does specify a number of procs, we will sequentially
map that number of procs, one to each entry in the hostfile. Multiple
app_contexts are supported, with the sequence continuing across the
app_contexts.

5. if you specify a number of procs greater than the number of entries in
your hostfile, we will map the overrun using byslot rules - i.e., we will
start by filling the remaining slots on the first node in your hostfile,
then proceed to fill the second node in your hostfile, etc.

6. if your allocation does not permit oversubscription, we will report an
error and abort if you attempt to place more procs on a node than slots.

Hope that helps
Ralph