Charm++ parallel programming system

[Gengbin Zheng <zhenggb AT gmail.com>]

When you said "ll get different answers for +p4 and +p8 ", do you mean
you get different NQueens result, or the execution time is different.

If it is the former, it must be a bug.
If you meant different execution time, that is expected.

You can oversubscribe a physical cores for multiple processes,
however, the context switching overhead of processes are expensive.
The more you oversubscribe the cores, the higher overhead you may get.
The advantage of Charm++ virtualization (i.e. use light-weight object
and user-level threads) are much more efficient compared to the
process level oversubscription .

Gengbin


On Tue, Jan 10, 2012 at 12:40 PM, Balaji S 
<balaji.ceg.13 AT gmail.com>
 wrote:
> Hi sir,
>         Thanks for the prompt reply. But my doubt is, when i run the example
> program "nqueens" with "./pgm 12 6 +p4"
> and "./pgm 12 6 +p8" I get different runtime , but i have "intel i3
> processor running on 64 bit ubuntu 10.04", if +p is real
> processors, how i ll get different answers for +p4 and +p8 ( since i don hav
> even 4 cores/processors) ?
>
> Regards,
> Balaji Sekar
>
>
> On Tue, Jan 10, 2012 at 12:45 PM, Celso L. Mendes 
> <cmendes AT illinois.edu>
> wrote:
>>
>> The "+p" parameter indicates the number of physical (i.e. real)
>> processors where the program will be running.
>>
>> There is another parameter, "+vp", which indicates the number
>> of virtual processors. Thus, you can run, say, with "+p 8 +vp 128"
>> where each physical processor will be in charge of 16 virtual
>> processors.
>>
>> BigSim explores this capability to simulate future machines.
>> Each virtual processor assumes the role of a target processor
>> of the future machine. In the example above, you would be using
>> a current machine with 8 existing processors to simulate a future
>> machine with 128 processors.
>>
>> -Celso
>>
>>
>>
>> On 1/10/2012 11:30 AM, Balaji S wrote:
>>>
>>> Hi ,
>>>
>>> I am new to charm++. I have read that bigsim is used to simulate more
>>> number of processors,
>>> When in charm++, u can specify the option (as a commandline argument )
>>> +p8 or +p32 to indicate
>>> number of processors, what is need for a separate simulator like bigsim?
>>>
>>> --
>>> With Regards,
>>> Balaji.S
>>>
>>>
>>>
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>>>
>>>
>>>
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>>
>>
>
>
>
> --
> With Regards,
>     Balaji.S
>
>
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-- 
--------------------------------------------
 Gengbin Zheng,  Ph.D.
 Research Scientist
 Parallel Programming Laboratory
 Department of Computer Science
 University of Illinois at Urbana-Champaign
 201 N. Goodwin Ave.
 Urbana, IL 61801