[torquedev] nodes, procs, tpn and ncpus

[Martin Siegert]

On Fri, Jun 11, 2010 at 09:59:47AM -0600, Ken Nielson wrote:
> 
>    On 06/10/2010 09:36 PM, Christopher Samuel wrote:
> 
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>    On 11/06/10 04:47, Glen Beane wrote:
>    > In my opinion, I think nodes=X,procx=Y should generate
>    > a syntax error...
>    Agreed.
>    I am not swayed one way or another yet. What if a user makes a request
>    like the following
>    -l nodes=4:ppn=2+procs=6
>    The user wants four nodes with two processors each and then 6
>    processors anywhere they are available.
>    -l nodes=4+procs=4
>    The user wants 4 nodes plus 4 processors anywhere. This one makes less
>    sense than the first, but if we allow the first we need to allow this
>    as well.
>    Thoughts anyone?

It all depends on whether we want to break the meaning of nodes=N being
totally equivalent to nodes=N:ppn=1.
1) if we stick to the meaning of nodes=N just being a shorthand for
   nodes=N:ppn=1 then -l nodes=4+procs=4 makes just as much sense as
   nodes=4:ppn=2+procs=6, i.e., there is no problem.
2) if we change the meaning of nodes=N to become "give me exclusive
   access to N nodes" then we need to define what -l nodes=N+procs=M
   means.

I actually vote for (1). E.g., what is the default if neither nodes nor
procs is specified? Currently that is nodes=1:ppn=1, i.e., the default
for nodes is 1 and the default for ppn is one. That logical extension is
that if only nodes is specified then the default value for ppn should be
used. I.e., nodes=N means nodes=N:ppn=1.
But that leaves us with the problem of how to specify exclusive access
to a node. What about a keyword ALL as in nodes=4:ppn=ALL ? It is a
logical extension of the current syntax and is easy to understand.
And then things like -l nodes=1:ppn=ALL+procs=42 make total sense
(at least to me).

Cheers,
Martin