Dear Prof. McCalpin,
I am a little puzzled by the results of your "bandwidth" benchmark, and I
wonder if you could explain them to me. In a nutshell, I don't see how
you get the memory bandwidth figures from the results of running your
program.
I have some money to invest in a machine to do serious numerical
calculations which are pretty memory -intensive and so I am keenly
interested in the results. I would also be very interested in your
opinions of the various competitors. I am looking at IBM/HP/DECAlpha
/SGI Challenge machines.
You may be interested in my benchmarking results for these and other
machines. The program is a MD simulation code written by me in C.
The comparison of the "small", ie in-cache runs with the "big" 30MB
ones is *very* revealing and does sort out the sheep from the goats.
If so, just get the file "/pub/benchmark.tex" by anonymous ftp from
earth.ox.ac.uk (or eeyore.earth.ox.ac.uk or 163.1.22.1 -- we changed
our DNS records recently and it may not have propagated yet).
In any case I have some results from running your benchmark for
DEX Alpha/HP 755/735 and STardent Titan P3. My titan results differ
substantially from those you have reported -- I don't know why.
But my results agree well with the theoretical bus bandwidth
of 256 MB/sec.
sincerely
Keith Refson
--------------------------------------------------
Here are the results.
HP 755/735
feynman 22: ./a.out
--------------------------------------
Double precision appears to have 16 digits of accuracy
Assuming 8 bytes per DOUBLEPRECISION word
--------------------------------------
Timing calibration ; time = 21.00000046193599 hundredths of a second
Increase the size of the arrays if this is <30
and your clock precision is =<1/100 second
---------------------------------------------------
Function Rate (MB/s) RMS time Min time Max time
Assignment: 68.5715 .0700 .0700 .0700
Scaling : 68.5715 .0700 .0700 .0700
Summing : 72.0001 .1021 .1000 .1100
SAXPYing : 80.0001 .0971 .0900 .1000
DEC 3000/500 (150MHz AXP Alpha)
axpbb% ./a.out
--------------------------------------
Double precision appears to have 16 digits of accuracy
Assuming 8 bytes per DOUBLEPRECISION word
--------------------------------------
Timing calibration ; time = 16.49440079927444 hundredths of a second
Increase the size of the arrays if this is <30
and your clock precision is =<1/100 second
---------------------------------------------------
Function Rate (MB/s) RMS time Min time Max time
Assignment: 100.3680 0.0485 0.0478 0.0488
Scaling : 96.4323 0.0499 0.0498 0.0508
Summing : 98.3607 0.0736 0.0732 0.0742
SAXPYing : 99.6900 0.0730 0.0722 0.0732
Kubota (ex Stardent Titan P3 ) 1processor
zebedee% a.out
--------------------------------------
Double precision appears to have 16 digits of accuracy
Assuming 8 bytes per DOUBLEPRECISION word
--------------------------------------
Timing calibration ; time = 37.00000196695328 hundredths of a second
Increase the size of the arrays if this is <30 and your clock precision is =<1/100 second
---------------------------------------------------
Function Rate (MB/s) RMS time Min time Max time
Assignment: 240.0002 0.0265 0.0200 0.0300
Scaling : 240.0002 0.0283 0.0200 0.0300
Summing : 239.9993 0.0391 0.0300 0.0400
SAXPYing : 144.0001 0.0522 0.0500 0.0600
Kubota (ex Stardent Titan P3 ) 4 processors
zebedee% a.out
--------------------------------------
Double precision appears to have 16 digits of accuracy
Assuming 8 bytes per DOUBLEPRECISION word
--------------------------------------
Timing calibration ; time = 79.99998927116394 hundredths of a second
Increase the size of the arrays if this is <30 and your clock precision is =<1/100 second
---------------------------------------------------
Function Rate (MB/s) RMS time Min time Max time
Assignment: 480.0005 0.0228 0.0100 0.0300
Scaling : 240.0002 0.0349 0.0200 0.0900
Summing : 240.0002 0.0363 0.0300 0.0400
SAXPYing : 240.0002 0.0449 0.0300 0.0600
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