Timing (was wordOffset, repeat loop, speed?

[Dar Scott]

On Monday, January 6, 2003, at 07:54 AM, Glasgow, David wrote:

> It may be that things have moved along a bit, or I am getting 
> something wrong ....I'd be interested in any comments.

Computers and timers are a lot more accurate.

It is true that interrupts and system threads are running all the time 
and the time you measure will often be higher than what you want to 
look at (in some sense).

If you are timing a one second operation you _will_ be including some 
system overhead in measurement.  The precision timing may not mean much 
here.  If you take lots of measurements and average those you will have 
the effective time in that environment, hardware and OS.

If you are measuring very short times you need the precision.  In this 
case, you can average.  Make sure you throw out the outliers.  Or you 
can take the minimum of several time trials.  This tends to remove the 
effect of the OS, so you cannot compare to the times from the longer 
time method above.  This does allow you to make some decisions in 
coding style.

The minimum method may provide a useful measure for long periods also, 
depending on your use, but it will always include some system overhead 
time.

In my method for measuring short times, I use the same command for 
getting the time before and after the operation to be measured.  I also 
use that for measuring doing nothing, effectively measuring the time to 
make a measurement.  I subtract that from my results.

Dar Scott