Re: [Gems-users] Average packet latency VS. Ruby cycles

[Miray Kas <miraykas@xxxxxxxxx>]

Network latency is not the only component that contributes to the overall execution time. The further reduction might be coming from other components.

On Tue, Aug 24, 2010 at 11:04 PM, fubinzhang <fubinzhang@xxxxxxxxx> wrote:

Hi all,

       Recently, we simulate a new routing algorithm on GEMS with splash2,
and I get puzzled about the results.

For example, for application LU-non-contiguous, our routing algorithm
reduces the average packet latency by 7% compared with the default xy
routing.

However, the ruby cycles is reduced as much as 11%.

I remembered Dan has pointed out the performance uncertainty of parallel
applications. So, I run this application twice, but got the similar results.

How does this happen? Can 7% packet latency reduction lead to 11% execution
time reduction? Is it reasonable?

Thanks in advance.


P.S.
Network Topology: 4x4 mesh
Cache Protocol: MSI_MOSI_CMP_directory
VC per VN: 1
VC buffers: 4
Flow control: We modify the flow control to set an output unit free as soon
as the tail flit has been sent. Then, the VCallocator selects an output unit
once it is free, as well as it has credit.


Regards,

Fbz.

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