[SAGA-RG] quick poll: SPMD attributes

[Andre Merzky]

Hi Ole, 

Quoting [Ole Christian Weidner] (Dec 10 2009):
> 
> > Some of the concerns may get addressed by resource discovery and
> > reservation, but not all.  So, we would like to propose the
> > following replacement list for these attributes:
> > 
> >  SPMDVariation
> >  NumberOfProcesses
> >  ProcessesPerMachine
> >  ProcessesPerSlot
> >  ProcessesPerCore
> > 
> > (Slot and Machine are the DRMAA terms for CPU and Host).
> 
> Let's go with CPU and host then. Especially slot is IMHO a rather weird term - cpu is so much easier to understand. 

Peter corrected me: its socket, not slot.  Anyway, I am by no means
sold to those terms, but rather want to nail down concept and
hierarchy.  Machine and CPU would be fine with me, as would be

  node
  host
  machine

and

  cpu
  socket
  processor


> > The NumberOfProcesses is to be interpreted as exact number by the
> > backend.  The ProcessesPerXYZ are to be interpreted as upper bounds
> > by the backend.  
> > 
> > So, for example, one could specify a 16 process MPICH job as
> > 
> >  SPMDVariation     = MPICH
> >  NumberOfProcesses = 16
> >  ProcessesPerCore  = 2
>
> Ok, but what if the backend doesn't understand these things, (RSL
> for example only understands number of nodes and number of
> processes). In this case the adaptor itself would have to (a)
> figure out the number of cores per cpu (b) the number of cpus per
> node and (c) make a reservation for
> (16/2/#cores_per_cpu/#cores_per_node) nodes. The globus GRAM
> adaptor already does something similar to this due to the
> shortcomings of RSL. Not pretty. 

Right - but it is even worse if the user has to do it on application
space.  So, I guess it is like with all other JD attributes: if it
is specified, it must be honored - which may effectively limit the
number of available backends...


> And the more possible attributes you have, the more options you
> give the user to define the same thing. E.g

eg? :-)

Thanks!  Andre.




-- 
Nothing is ever easy.