[Beowulf] Thought that this might be of interest

[Bill Broadley]

Joe Landman wrote:
> We are working on a machine with 2 Opteron 2218s.  For laughs, I ran 
> streams on it.  Here are 1,2,3,4 processor data.

I have a opteron 2220 handy with DDR2-667.  At least I'm pretty sure
it's DDR2-667.  I multiplied the default N by a factor of 10 to get timings 
similar to yours.

> 1 processor:
> Copy:       5713.9944      0.0591      0.0560      0.0600
> Scale:      5713.9822      0.0587      0.0560      0.0600
> Add:        5454.2389      0.0911      0.0880      0.0920
> Triad:      5454.1576      0.0916      0.0880      0.0920

Function      Rate (MB/s)   Avg time     Min time     Max time
Copy:        6615.1324       0.0484       0.0484       0.0484
Scale:       6665.6930       0.0480       0.0480       0.0481
Add:         6147.8462       0.0781       0.0781       0.0781
Triad:       6175.3782       0.0777       0.0777       0.0778


> 2 processors:
> 
> Function     Rate (MB/s)  Avg time   Min time  Max time
> Copy:       5713.8788      0.0591      0.0560      0.0640
> Scale:      5713.9822      0.0596      0.0560      0.0640
> Add:        5713.9538      0.0858      0.0840      0.0880
> Triad:      5713.9538      0.0871      0.0840      0.0880

Obviously using 2 sockets (not 2 cores on 1 socket):

Function      Rate (MB/s)   Avg time     Min time     Max time
Copy:       11836.5091       0.0270       0.0270       0.0270
Scale:      11685.2307       0.0274       0.0274       0.0274
Add:        11923.6815       0.0403       0.0403       0.0403
Triad:      11972.4659       0.0401       0.0401       0.0401

> 4 processors:
> 
> Copy:      11428.1834      0.0293      0.0280      0.0320
> Scale:     11428.1347      0.0298      0.0280      0.0320
> Add:       10908.5812      0.0449      0.0440      0.0480
> Triad:     10908.6107      0.0440      0.0440      0.0440

Function      Rate (MB/s)   Avg time     Min time     Max time
Copy:       12828.7019       0.0250       0.0249       0.0251
Scale:      12942.8860       0.0248       0.0247       0.0249
Add:        12910.1852       0.0374       0.0372       0.0377
Triad:      13030.0040       0.0369       0.0368       0.0372

> I did get one outlier at 4 CPUs.  Could be a timing glitch.
> 
> 4 processors:
> Copy:      13332.7765      0.0302      0.0240      0.0360
> Scale:     13332.7765      0.0262      0.0240      0.0320
> Add:       13332.6220      0.0400      0.0360      0.0480
> Triad:     14999.0756      0.0391      0.0320      0.0480

Your timer does look dramatically less accurate than mine. The granularity
of yours looks to be around 0.0040.  Where mine is 0.0001 or so.  My
runs were pretty consistent.  Notice that many of my min, max, and averages
are the same.