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Re: Assignment Time for a 3d Variable [message #46473 is a reply to message #46470]

Wed, 23 November 2005 08:52

David Streutker
Messages: 34
Registered: June 2005

Member

David Fanning wrote:
> The speed differences have to do with how you access different
> parts of the array in memory. If the parts you want are contiguous,
> then you can get them faster than you can if they are far apart in
> memory. (Think how much faster it is to pick up the poker
> chips when they are stacked than when they are scattered all
> around the table.)
>
> To make these kinds of assignments as fast as possible, use
> the TRANSPOSE function to organize the data into the fastest
> possible position:
>
> IDL> Help, data
> DATA BYTE = Array[3, 227, 149]
> IDL> data = Transpose( Temporary(data), [2,3,1] )
> IDL> Help, data
> DATA BYTE = Array[227, 149, 3]

How does one know which is the fastest possible position? Should the
largest dimension be first? Nuno's example seems to imply that the
first dimension is not the fastest accessed.

-Dave

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[Message index]

		Re: Assignment Time for a 3d Variable By: Mark Hadfield on Wed, 23 November 2005 12:17
		Re: Assignment Time for a 3d Variable By: Foldy Lajos on Wed, 23 November 2005 11:13
		Re: Assignment Time for a 3d Variable By: David Fanning on Wed, 23 November 2005 11:09
		Re: Assignment Time for a 3d Variable By: James Kuyper on Wed, 23 November 2005 10:35
		Re: Assignment Time for a 3d Variable By: K. Bowman on Wed, 23 November 2005 10:16
		Re: Assignment Time for a 3d Variable By: Antonio Santiago on Wed, 23 November 2005 09:51
		Re: Assignment Time for a 3d Variable By: David Streutker on Wed, 23 November 2005 08:52
		Re: Assignment Time for a 3d Variable By: David Fanning on Wed, 23 November 2005 07:57
		Re: Assignment Time for a 3d Variable By: Antonio Santiago on Wed, 23 November 2005 04:46

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