[Fwd: 8 node cluster help!]

[Patrick Geoffray]

nate fuhriman wrote:
 
> This is the result with a data size of 4000. 8000 crashed the machine.
> Remember this is with HEAVY swapping because it was on a single machine.
> (hd light was constant)

> W00L2L2         4000     1     2     2           52143.23          8.187e-04

If it's swapping, it's normal that the performance is bad, like
everywhere in the HPC world. A matrix of 4000 needs (4000*4000*8) = 125
MB at the application level. 
The benchmark uses also 4 processes (2x2) : if it's on a single machine,
I hope you have 4 processors in the box ;-)

To forecast the result of HPL (High perf Linpack), you can take the peak
of DGEMM reported by ATLAS, multiply it by the number of processors and
then multiply by 0.75 (rough efficiency of 75 %, may be 50 % for cheap
interconnect) to get the total performance. So 8 nodes with a Pentium
III at 550 MHz, assuming that your are using ATLAS to generate the BLAS
and you have enough memory in each boxe to reach a point close of the
DGEMM peak, should get something between 4 and 6 GFlops.

If any machine swaps, the performance goes to the toilettes :-))

Hope it helps.

-- 
Patrick Geoffray

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