[mpich-discuss] Clock synchronization

[Pavan Balaji]

[please keep mpich-discuss cc'ed].

There is no real communication during synchronization. Zero-byte 
messages are exchanged. The algorithm used is logarithmic with respect 
to the number of processes.

  -- Pavan

On 04/02/2011 02:52 AM, Ravi Prakash wrote:
> Thanks Pavan! :) Do you know if synchronization is done by splitting the
> communication time in half or somesuch algorithm?
>
> Cheers
> Ravi
>
> ------------------------------------------------------------------------
> *From:* Pavan Balaji <balaji at mcs.anl.gov>
> *To:* Ravi Prakash <ravihoo at ymail.com>; mpich-discuss at mcs.anl.gov
> *Sent:* Friday, April 1, 2011 11:33 PM
> *Subject:* Re: [mpich-discuss] Clock synchronization
>
>
> Assuming TCP/IP communication and a 10-20 machines, once you do an
> MPI_Barrier, I don't expect the time difference between the machines to
> be more than a few 10s of microseconds, if not lesser.
>
> -- Pavan
>
> On 04/01/2011 11:28 PM, Ravi Prakash wrote:
>  > Hi,
>  >
>  > I'm a n00b and I'm wondering if there is any documentation on what clock
>  > synchronization algorithm MPICH2 uses. I need to trigger events at the
>  > same time across multiple machines. What accuracy am I looking at?
>  >
>  > My machines are Windows Vista boxes with Dual dual-core Xeons connected
>  > by an ethernet 100Mbps LAN. Please let me know if there are any more
>  > relevant factors needed for an approximate figure. Is it a few ms / 10's
>  > of ms / 100's of ms / god forbid seconds? :)
>  >
>  > Cheers
>  > Ravi
>  >
>  >
>  >
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>
> --
> Pavan Balaji
> http://www.mcs.anl.gov/~balaji
>
>

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji