| Re: Large Arrays in IDL [message #5533] |
Mon, 15 January 1996 00:00  |
hahn
Messages: 108
Registered: November 1993
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Senior Member |
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Eric Deutsch <deutsch@astro.washington.edu> wrote:
[several paragraphs deleted]
> IRAF was designed to be able
> to work with large image arrays without much memory. You can write IDL
> routines to do this, too, but it is usually much simpler to give your
> computer a huge chunk of virtual memory, with 1 GB disks costing well under
> $300 these days...
IDL can work with arrays directly on disk by using the Associate
Variable. You open a file as you would for normal input or output
and call the IDL function ASSOC to combine the i/o unit number,
an array of needed type and size and get a variable as a result
of the function call, the associate variable. Each time the associate
variable appears on the right side of an IDL expression or as a
parameter for TV a chunk of the array is read from disk and processed.
Each time the associate variable appears on the left side of an
expression the file on disk will be written.
The was some discussion on memory usage. If I'm not mistaken
the amount of virtual storage you can use with any MS Windows 3.1
application is 2.5 times the RAM of your computer. This may no longer
be true for Windows 95, I couldn't check it.
> Eric
> --
> ------------------------------------------------------------ ----------------
> Eric Deutsch email: deutsch@astro.washington.edu
> Department of Astronomy Voice: (206) 616-2788
> University of Washington FAX: (206) 685-0403
> Box 351580 WWW: http://www.astro.washington.edu/deutsch
> Seattle, WA 98195-1580 Physics/Astronomy Bldg., Room B356F
Norbert Hahn
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