[Beowulf] Opinions of Hyper-threading?

Mark Hahn hahn at mcmaster.ca
Thu Feb 28 15:45:52 EST 2008


> How do your Rate numbers correlate to the max bandwitdh of 32GB/s
> (http://en.wikipedia.org/wiki/GeForce_8_Series)?

good point.  I had assumed the quoted numbers were merely in-cache,
but it does claim to be running on array size 2e6 (8e6 bytes),
which seems a bit large for in-cache.  (though very small for a Stream run).

>> http://forums.nvidia.com/index.php?showtopic=52686

this quotes a plausible 64-65 GB/s on a C870 (76.8 peak theoretical).

>> Running this on my 8600 card I get:
>>
>> STREAM Benchmark implementation in CUDA
>>  Array size (single precision)=2000000
>>  using 128 threads per block, 15625 blocks
>> Function      Rate (MB/s)   Avg time     Min time     Max time
>> Copy:      291777.6696       0.0001       0.0001       0.0001
>> Scale:     291777.6696       0.0001       0.0001       0.0001
>> Add:       437666.5043       0.0001       0.0001       0.0001
>> Triad:     437666.5043       0.0001       0.0001       0.0001

this is implausible.  my guess is the timing code is broken.
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