[jsdl-wg] Process Topology

[Andreas Savva]

Karl Czajkowski wrote:
> On Apr 20, Andreas Savva loaded a tape reading:
> 
> 
>>I meant that if a resource description is given as
>><Resource>
>>  <CPUCount> <Exact> 2.0 </Exact>  </CPUCount>
>></Resource>
>>
>>it means a 2-cpu host. Not 2 CPUs from a possibly larger N CPU machine.
>>
> 
> 
> Yes, this is indeed the "latter" case from Chris.  I had hoped we
> didn't care about the aspects of a resource _not_ allocated to us.
> 
> Why do you actually care whether your 2 CPUs are a whole host or not?
> Is this actually some sort of selection preference sneaking in, like
> do not give me the more rare nodes?  Or is it a QoS issue like
> "exclusivity" of the resource?  I think it is important that we
> understand why you want to express this, now that it is clear what you
> are expressing.
> 
> Do you expect to express similar physical constraints on other
> resources not necessarily allocated to you, e.g. amount of RAM or
> virtual memory space not necessarily allocated to you?  I'm not trying
> to be snarky but this avenue does confuse me lots!

My requirement is very simple. If I ask for a 2-way SMP machine I want a 
  2-way SMP machine and nothing else. It is not a preference. Consider 
that I may want to run software specifically tuned to some configuration 
(cpu, ram, and so on) and I don't want the system to be 'helpful' and 
give me something that it thinks is better for me. Unless I tell it so 
by using a range expression.

Obviously this has nothing (or doesn't necessarily) have to do with 
'process topology.'


> 
> 
> 
>>If on the other hand I said
>><Resource>
>>  <CPUCount> <LowerBoundedRange> 2.0 </LowerBoundedRange>  </CPUCount>
>></Resource>
>>
>>I would accept any machine with at least 2 CPUs.
>>
> 
> 
> I find this ambiguous again... you need to distinguish again
> acceptance of an allocation from acceptance of characteristics of a
> resource that have not been allocated to you!

Not sure what was ambiguous; maybe the "I would accept.." part? Perhaps 
I should say instead that the above fragment to me means "I want a host 
with at least 2 cpus."

> 
> 
>>So the (my?) definition would be closer to Chris' second definition.
>>
>>Maybe we should leave the rest until we can clarify what is the correct 
>>definition of resource multiplicity (and what other people think the 
>>correct meaning of the above fragments are....)
>>
>>Andreas
>>
> 
> 
> It seems to me the issue of resource element mulitplicity is
> orthogonal... it is whether we support heterogeneous resource
> requirements or not, e.g. some number of resources that look like THIS
> and some other number of resources that look like THAT.

I agree that we are mixing in too many concepts. For 'process topology' 
let's just focus on a single resource element.

> 
> As for you parenthetic comment, I think it is useless to investigate
> "what people think the correct meaning of [...] fragments are" but
> rather we should focus on what meanings do we want to convey in JSDL
> and then fix the syntax to do so unambiguously.

True. But I assume (hope rather) there is already some consensus on what 
those fragments mean and would hate to try to start from scratch.


> 
> It sounds to me like you are advocating the full set of concepts I
> suggested in my earlier message:

I think we are not that far apart. Just to map these to what I've been 
using:

> 
>   allocated CPUs per resource

I guess 'similar' to TileSize at the moment.

>   total allocated CPUs 

'ProcessCount' I guess.

> 
>   installed CPUs per resource (your 2-cpu machine)

CPUCount

> 
> As Chris said, using range value expressions on "allocated CPUs per
> resource" will give us tile size, e.g. I want 2,4,8,16 CPUs per
> resource (but not 7 etc.) and I want between 32 and 128 CPUs total.
 >
> One thing that confuses me is whether there needs to be a way to
> express symmetry or "strict homegeneity" e.g. 
> 
>    4 nodes, each with 4 cpus
>      OR
>    4 nodes, each with 8 cpus
> 
> versus
> 
>    4 nodes, each with 4 or 8 cpus
> 
> I think the latter is what we know how to express right now using
> exact resource counts, by considering them equivalent to unrolling
> into a fixed number of resource elements.  I do not know if others
> intended this or the stricter symmetric interpretation.
> 
> karl

Yes. What we have in the spec right now can express the latter version 
but not the former. We don't have an 'OR' operator. I think the former 
is where we should start to be thinking of combining JSDL with other 
specs like WS-Agreement.


-- 
Andreas Savva
Fujitsu Laboratories Ltd