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Re: Code optimization [message #75200 is a reply to message #75116]

Thu, 17 February 2011 12:52

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article
<ff8c9322-c3c0-4ed0-b9c2-73ae36c71a16@g10g2000vbv.googlegroups.com>,
kisCA <kis93@hotmail.com> wrote:

> Jeremy, I am amazed how you manage so quickly to find a way to
> optimize the code. Do you have some tips to achieve it?

Here is my short list of priorities for code optimization in IDL:

Optimize where it matters - Don't worry about optimizing code
that does not affect the overall cpu time.
Do binary I/O - NetCDF, HDF, or binary, not ASCII.
Access memory in order - Think about the order in which you are
likely to access your data before you define arrays. This will
make better use of caches in modern cpus.
Use IDL built-in functions and operators - There are many
tricks for using REBIN, REFORM, and HISTOGRAM, but be aware
that they are often memory intensive.
Optimize your innermost loop - Loops are not necessarily bad
in IDL if the calculations within a loop are well optimized.
Don't do unnecessary calculations (e.g., move constants out of loops)
Buy the IMSL library if you need those functions - Your time is
probably much more expensive than an IMSL license.

If you keep those things in mind, you will rarely have to resort
to the code profiler or external modules.

This seems sure to start a discussion. ;-)

Ken Bowman

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[Message index]

		Re: Code optimization By: Jeremy Bailin on Thu, 17 February 2011 11:52
		Re: Code optimization By: kisCA on Thu, 17 February 2011 11:42
		Re: Code optimization By: Fabzou on Thu, 17 February 2011 01:14
		Re: Code optimization By: Jeremy Bailin on Wed, 16 February 2011 13:48
		Re: Code optimization By: kisCA on Wed, 16 February 2011 13:25
		Re: Code optimization By: kisCA on Wed, 16 February 2011 13:23
		Re: Code optimization By: Jeremy Bailin on Wed, 16 February 2011 12:57
		Re: Code optimization By: pgrigis on Wed, 16 February 2011 12:51
		Re: Code optimization By: Kenneth P. Bowman on Thu, 17 February 2011 12:52
		Re: Code optimization By: pgrigis on Thu, 17 February 2011 12:09

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