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Re: Dealing with Large data arrays, reducing memory and ASSOC [message #54462 is a reply to message #54460]

Thu, 14 June 2007 09:32

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Thu, 14 Jun 2007 08:08:44 -0500, Kenneth Bowman wrote:

> In article <1181824433.145388.26020@d30g2000prg.googlegroups.com>,
> Ambrosia_Everlovely <ambrosia_everlovely@hotmail.com> wrote:
>
>> [quoted text muted]
>
> I would just do it in slices
>
> dct = COMPLEXARR(512,512,2048)
> FOR j = 0, 511 do dct[*,j,*] = FFT(REFORM(dc[*,j,*]), -1, DIM = 2)
>
> This does access memory in nearly the worst possible way. If you are
> going to be doing this a lot, you might want to consider rearranging the
> data so that t is the first dimension
>
> dct = COMPLEXARR(2048,512,512)
> FOR k = 0, 255 D0 xt[0,0,k] = FFT(REFORM(x[*,*,k]), -1, DIM = 1)

I'd be interested to hear whether this "in order" type of array
re-arrangement results in a real speedup. I had always assumed this
is true, but in recent testing on a very different problem, found
little or no gain, to my surprise.

JD

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[Message index]

		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Kenneth Bowman on Fri, 15 June 2007 12:54
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: bill.dman on Fri, 15 June 2007 11:40
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Ambrosia_Everlovely on Fri, 15 June 2007 00:26
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Kenneth Bowman on Thu, 14 June 2007 11:52
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Kenneth Bowman on Thu, 14 June 2007 11:50
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: JD Smith on Thu, 14 June 2007 09:32
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Haje Korth on Thu, 14 June 2007 09:18
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: bill.dman on Thu, 14 June 2007 06:41
		Re: Dealing with Large data arrays, reducing memory and ASSOC By: Kenneth Bowman on Thu, 14 June 2007 06:08

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