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Re: Assignment Time for a 3d Variable [message #46463 is a reply to message #46459]

Wed, 23 November 2005 11:13

Foldy Lajos
Messages: 268
Registered: October 2001

Senior Member

Hi,

Fortran is column major, IDL and C are row major. In IDL (unlike C or
Fortran) the first subscript is column, not row.

It is best not to refer to Fortran or C, IDL is like IDL :-)

regards,
lajos

On Wed, 23 Nov 2005, Kenneth Bowman wrote:

> In article <1132768280.23827.0.camel@localhost.localdomain>,
> Antonio Santiago <santiago@grahi.upc.edu> wrote:
>
>> Also I note that it depends on the language IDL is implemented. By
>> default all ANSI C compilers use row major mode.
>> See the other post for the link to an example :)
>
> IDL uses the Fortran convention for storage of arrays, that is, the first
> subscript varies fastest.
>
> "The fact that the elements of the first dimension are contiguous means that the
> elements of each row of an image array are contiguous. This is the order
> expected by most graphics hardware, providing an efficiency advantage for
> languages that naturally store data that way. Also, this ordering minimizes
> virtual memory overhead, since images are accessed linearly."
>
> Ken Bowman
>

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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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