On 11/7/07, Anthony Chan <chan@mcs.anl.gov> wrote:

The clocks ain't synchronized in most clusters.
MPE logging does clock alignment to align the timestamps based on a
send/recv based synchronization algorithm whose accuracy is limited by
latency of the network (which could be noise, hence even less accurate).
If your cluster has a global clock, you could disable the sync code by
setting the environment variable MPE_CLOCKS_SYNC=false, default is true.
If your run involes more than 16 processes, the sync algorithm may not be
the most accurate. In that case you can choose a better one (See
mpe2/README). In general, it does not make much difference.

BTW, you shouldn't send zero byte message, :)

A.Chan

On Wed, 7 Nov 2007, Apurva Bhatnagar wrote:

> Hey are u talking about system clocks , which are different in heterogeneous
> clusters...
>
> On 11/7/07, Apurva Bhatnagar <apurvanarayan@gmail.com> wrote:
>>
>> But can this be solved. i am using 7.1.4 i think...
>>
>> On 11/7/07, Anthony Chan <chan@mcs.anl.gov> wrote:
>>>
>>>
>>> What version of MPE are you doing ?
>>>
>>> Do you mean your arrow is pointing backward when message size is zero ?
>>> If this is the case, this is probably due to the clock synchronization
>>> algorithm isn't accurate enough for the given MPI_Wtime resolution.
>>> If this is the only case that you see backward arrow, I don't think
>>> you need to worry about it.
>>>
>>> A.Chan
>>>
>>>
>>> On Wed, 7 Nov 2007, Apurva Bhatnagar wrote:
>>>
>>>> Dear Sir,
>>>> I am running LAM /MPI on my code on DE algorithm which requires string
>>>> evaluations which i do it on multiple computers . I am facing a
>>> problem with
>>>> Jumpshot results.When i am using a uniform (homogeneous cluster) my
>>> results
>>>> seem ok but when i use a heterogeneous cluster some time i face
>>> problem that
>>>> my message send time becomes negative and message size becomes
>>> ZERO..what
>>>> does it signify,
>>>> Shall i send in the printscreen of the jumpshot if its needed.
>>>> Regards
>>>> Apurva
>>>>
>>>>
>>>>
>>>> --
>>>> " Life is a BICYCLE the more you work the faster you GO!! "
>>>>
>>>> Apurva Narayan
>>>> Final Year Electrical Engg,
>>>> Faculty of Engineering,
>>>> Dayalbagh Educational Institute,
>>>> Agra - 5
>>>> Ph: +91-9412605116
>>>> Email : apurvanarayan@ieee.org
>>>> Web : http://appu.netfirms.com
>>>>
>>> _______________________________________________
>>> This list is archived at http://www.lam-mpi.org/MailArchives/lam/
>>>
>>
>>
>>
>> --
>> " Life is a BICYCLE the more you work the faster you GO!! "
>>
>> Apurva Narayan
>> Final Year Electrical Engg,
>> Faculty of Engineering,
>> Dayalbagh Educational Institute,
>> Agra - 5
>> Ph: +91-9412605116
>> Email : apurvanarayan@ieee.org
>> Web : http://appu.netfirms.com
>>
>
>
>
> --
> " Life is a BICYCLE the more you work the faster you GO!! "
>
> Apurva Narayan
> Final Year Electrical Engg,
> Faculty of Engineering,
> Dayalbagh Educational Institute,
> Agra - 5
> Ph: +91-9412605116
> Email : apurvanarayan@ieee.org
> Web : http://appu.netfirms.com
>