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Re: Efficient sub array extraction [message #82404]

Wed, 12 December 2012 08:01

Heinz Stege
Messages: 189
Registered: January 2003

Senior Member

On Tue, 11 Dec 2012 16:00:35 -0800 (PST), markjamie@gmail.com wrote:

> Thanks for your responses. Glad to hear my subscripting was ok. You mention not to use arrays as subscripts - is there a reason for this?

Yes.

There is a big difference between using "subscript ranges", for
example
range=[10,110]
subarr=array[range[0]:range[1]]
or "array subscripts", for example
subscripts=indgen[101]+10s
subarr=array[subscripts]
The results are the same. But using array subscripts is typically
slower and needs more memory during the calculation of the subarray.
The difference may get very huge when subscribing multidimensional
arrays.

The reason probably is similar to the observation, discussed in the
article by David Fanning, cited by Phillip M. Bitzer in a previous
post within this thread. Please read it.

Heinz

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[Message index]

		Re: Efficient sub array extraction By: Heinz Stege on Wed, 12 December 2012 08:01
		Re: Efficient sub array extraction By: markjamie on Tue, 11 December 2012 16:00
		Re: Efficient sub array extraction By: Heinz Stege on Tue, 11 December 2012 15:41
		Re: Efficient sub array extraction By: David Fanning on Tue, 11 December 2012 15:40
		Re: Efficient sub array extraction By: Phillip M. Bitzer on Tue, 11 December 2012 14:34

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