[cadynce] How Many Configurations Is Enough?

[Gautam Thaker]

Raj Rajkumar wrote:
> Dear Joe:
> 
> These are very interesting analytical results.     Ideally, we should 
> keep going until the last machine is standing (ignoring I/O for this 
> discussion).   To tolerate such a high failure rate, your results show 
> that we need to store many more configurations (orders of magnitude 
> more).   Given that we cannot test a huge number of configurations 
> offline, it seems to me that we should have the ability to
> 
>    1. Generate feasible configurations on the fly given constraints at
>       that point in time.   Since the space of configurations can be
Hi Raj:

In my classification of DRM systems "on the fly" would count as "Box 3". 
Current approaches are based on "Box 2", which is to generate all 
certified allocations before hand. "Box 3" (on the fly generation) is 
easier at times, but would require enormous extra work of certifying the 
  allocators themselves (this is viewed as bridge too far for now, the 
worry is that Navy would be afraid fo this and I would agree.)

Gautam

>       large - albeit with scaling back requirements or running only the
>       most critical tasks that would fit, we should be able to find
>       one.  We do not have to find a feasible configuration if it
>       exists; we just have to find a reasonable one that will run under
>       the given constraints.
>    2. Assuming that the generated configuration in Step 1 has utilized
>       appropriate scheduling analysis etc., we need to have a high
>       degree of confidence that the dynamic run-time configuration we
>       chose will indeed run as predicted.  In that sense, we may want to
>       run experiments where a configuration generator is used to
>       generate configurations that have 'never' been tested, and show
>       that it can be run.   A 'tester' must be able to choose an
>       arbitrary configuration by tweaking parameters or making some
>       simple moves or swaps from a given configuration.   As has been
>       discussed before, the run-time environment must be adequately
>       reflected in the analytical model used during the generation of
>       feasible configurations.
> 
> Thanks,
> 
> ---
> Raj
> 
> Cross, Joseph wrote:
>> Gentledudes -
>>
>> On
>> https://escher.isis.vanderbilt.edu/twiki/bin/view/CADYNCE/Configurations
>> LoadsAndPerformance is a new section that quantifies computing system
>> survivability as a function of the degree of damage to the computing
>> plant and the number of configurations in our certified set. 
>>
>> Bottom line is that the good news for CADynCE is that if the computing
>> plant suffers 20% damage, then the difference between a set of 10 and a
>> set of 1000 allocations is the difference between life and death; the
>> bad news is that for 10% or less damage, and for 30% or more damage,
>> there is no material difference between 10 and 1000 allocations. 
>>
>> - Joe
>> ____________________________________
>> Dr. Joseph K. Cross, Program Manager
>> DARPA/IXO, room 612
>> 3701 North Fairfax Drive
>> Arlington, Virginia 22203-1714
>> joseph.cross at darpa.mil
>> (571) 218-4691
>>  
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> 
> 
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