Re: Fast matrix filling in IDL

[David Ritscher <david.ritscher(at)bigfoot.com>]

> Hopefully everyone is running this a few times and noting when
> the times have become "stable". Here are three sequential runs
> on a Sun Sparc 2 (IDL 5.1):
> 
> IDL> test
> Time for Loop:        2.7740721
> Time for Matrix Operations:        5.2337180     ; OUT OF WHACK!
> Time for Rebin Operations:       0.16969705
> IDL> test
> Time for Loop:        2.6756930
> Time for Matrix Operations:       0.27333605
> Time for Rebin Operations:       0.16920698
> IDL> test
> Time for Loop:        2.7509290
> Time for Matrix Operations:       0.27153599
> Time for Rebin Operations:       0.16843796


Perhaps the first one is not out of whack, but rather, the accurate
time.
When the test is being performed a second time, the operating system has 
information that is cached, thus avoiding doing part of the work
associated with the task.  Particularly in big tests, I often  notice
speed-ups each time, for the first few times I test something.  I like
to test by completely exiting my environment, doing other things, and
coming back and repeating the test.  If I'm feeling hard-core about it,
I do a reboot in between.


David Ritscher

-- 
Cardiac Rhythm Management Laboratory
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University of Alabama at Birmingham
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Email: david.ritscher@bigfoot.com