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Re: Strange memory problem [message #18423 is a reply to message #18337]

Wed, 22 December 1999 00:00

Alex Schuster
Messages: 124
Registered: February 1997

Senior Member

"R. Kyle Justice" wrote:

> When I do the following:
>
> temp=bytarr(1000,1000,25)
> temp(*)=10
>
> my computer (a Sparc20 with 128MB of *available* ram) grinds
> to a halt. Actually it starts using swap. Don't tell me
> PV-Wave is making 5 or 6 copies of the array just to do this
> simple process!
>
> Has anyone else seen this curious behavior on PV-Wave? IDL? I have
> verified it on a PC, and using different versions of PV-Wave(6.1,7.0).

Yes, I encountered the same problem. It seems that, when using the (*)
notation, IDL (and probably also PV-WAVE) replaces the * by an
appropiate index list, like here:

temp = bytarr(1000,1000,25)
index = lindgen(25000000L)
temp(index) = 10B

This index list takes 100 MB of memory! You can check this by the
command HELP, /MEMORY.

As others have pointed out, it is much faster when you use something
like this:
temp = bytarr(1000,1000,25)+10B
(Don't forget the B, because you would get an INTARR instead.)

This is much faster, and you need only 25 MB of RAM, as one would
expect.

Alex
--
Alex Schuster Wonko@weird.cologne.de PGP Key available
alex@pet.mpin-koeln.mpg.de

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[Message index]

		Strange memory problem By: rkj on Tue, 21 December 1999 00:00
		Re: Strange memory problem By: Terry Smith on Thu, 23 December 1999 00:00
		Re: Strange memory problem By: rivers on Thu, 23 December 1999 00:00
		Re: Strange memory problem By: jeyadev on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: Mark D. Williams on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: m218003 on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: Peter Mason on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: thompson on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: Julie Greenwood on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: Alex Schuster on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: thompson on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: Julie Greenwood on Wed, 22 December 1999 00:00
		Re: Strange memory problem By: rkj on Wed, 22 December 1999 00:00

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