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Re: Efficient sub array extraction [message #82420 is a reply to message #82418]

Tue, 11 December 2012 15:41

Heinz Stege
Messages: 189
Registered: January 2003

Senior Member

On Tue, 11 Dec 2012 14:26:40 -0800 (PST), markjamie@gmail.com wrote:

> I'm using large 2D arrays e.g 30000 x 30000 and need to remove a 2D sub array for later processing e.g. Rows 30-700 and columns 100-10000.
>
> Is there a more efficient way to do this than using subscript ranges?
>
> For example?
>
> Subarray = largearray[100:10000, 30:700]
>
>
> The exact code I'm using is as follows:
>
> A = [100,10000]
> B = [30,700]
>
> Subarray = largearray[A[0]:A[1],B[0]:B[1]]

Hi Mark,

from my point of view the use of subscript ranges is fine. (However do
not use arrays for subscripting.) Using subscript ranges is fast and
don't need much memory. In the following example roughly about 100
extra bytes are used at creating the subarray:

IDL> array=bindgen(30000,30000)
IDL> a=[100,10000]
IDL> b=[30,70]
IDL> help,/mem
heap memory used: 900729595, max: 900729989, gets: 1073, frees:
232
IDL> subarr=array[a[0]:a[1],b[0]:b[1]]
IDL> help,/mem
heap memory used: 901135568, max: 901135685, gets: 1085, frees:
243
IDL> print,!version
{ x86 Win32 Windows Microsoft Windows 8.0.1 Oct 5 2010 32
64}

Cheers, 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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