Dhrystone 2.0 timings

[Dick Dunn]

shawn at jdyx.UUCP (Shawn Hayes) writes:
>      I recently got a copy of the Dhrystone program V2.0 and ran it on our
> RS 320 machine.  The results aren't quite what IBM stated (using V1.0), but
> that shouldn't be a big suprise.  :>  I got a value of 11,881.2 dhrystones/sec
> using a non-optimized version, and a value of 18,867.9 dhrystones/second
> using the optimizer.  Averages out to about 11 MIPS which isn't bad.  

Hold on...this is a machine which is advertised at 27 MIPS, right?  And you
say 11 doesn't sound bad???

Let's recheck things here.  Are you sure you got the clock speed right?
The Dhrystone benchmarks depend on having the value HZ set properly (in 1.x
it's in the code; in 2.x it's in the Makefile).  Please do a sanity check,
and could someone else try to replicate the results?  The best "sanity
check" is to do "time dry2" to get the "time" command's idea of total CPU
time; then see if the benchmark's reported "Microseconds for one run"
times the number of iterations gives you about the right CPU time number.
ALSO, time it with your watch on a quiet machine (as an extra sanity check
on the time command:-).

I find it hard to believe that a machine could run less than half as fast
on a 2.x benchmark as on a 1.x benchmark.  I can believe 10% or maybe as
much as 20% degradation, but not 50%.  There must be something else going
on.

Let's see...if the machine has a 100 Hz clock and you ran the benchmark
with it set for 60, you'd be at about 31-32000 Dhrystones, which still
isn't enough.

>      In addition I decided to run another test today and ran 11 copies of the
> optimized version at the same time.  I got about 18,700 dhrystones/sec on
> 10 of the copies and about 14,000 on the last copy.  Not bad at all.

Hold it.  What's good about that?  Dhrystone is purely a CPU benchmark, and
it measures its results in CPU time.  It should give nearly the same
results regardless of machine load, but your results show something like a
1/3 increase in time (and only on one of the jobs, which is really
strange).
-- 
Dick Dunn     rcd at ico.isc.com    uucp: {ncar,nbires}!ico!rcd     (303)449-2870
   ...Don't lend your hand to raise no flag atop no ship of fools.