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Re: problems plotting LARGE amounts of 2D data? [message #1722 is a reply to message #1717]

Tue, 22 February 1994 18:36

peter
Messages: 80
Registered: February 1994

Member

Michael Cheng (mcheng@dunlop.cs.wisc.edu) wrote:

: Hi

: I am trying to find ways to plot LARGE amounts of 2D data,
: and I like to know what is currently the state of the art. For the
: sake of this posting, let's say "large" means much more data than
: fits in real memory. From my own experience, using the virtual memory
: of the workstation to store large amounts of data impedes performance
: due to excessive paging. Here is what I have been able to gather so far:

: 3)idl/pvwave: As far as I can tell from the short demo,
: loads everything into virtual memory?

IDL and PV-Wave have a 'associated' variable type, which lets you
map an array onto a disk file, and then step through the disk file
one slice at a time. For example,

openr, lun, 'myfile.dat', /get_lun
data = assoc(lun,bytarr(1024,1024))

associated the variable name data with the contents of file myfile.dat.
Nothing has been read yet. Then the statement

slice = data(10)

will load the 11th bytarr(1024,1024) contained in the file into working
memory. A statement like

data(10) = byte(fft(data(10)))

will read, process, and replace the 11th array in the disk file.

So, if you can access data in a nice order, so that you don't have to
go out to disk all the time, you can work with enormous data sets.

Something like this should also work for plotting a 2D data set.

Hope this helps.

- Peter

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[Message index]

		Re: problems plotting LARGE amounts of 2D data? By: jworley on Thu, 24 February 1994 13:51
		Re: problems plotting LARGE amounts of 2D data? By: thompson on Wed, 23 February 1994 12:20
		Re: problems plotting LARGE amounts of 2D data? By: peter on Tue, 22 February 1994 18:36
		Re: problems plotting LARGE amounts of 2D data? By: mcheng on Tue, 22 February 1994 14:51
		Re: problems plotting LARGE amounts of 2D data? By: thompson on Tue, 22 February 1994 09:22

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