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Re: Matrix expansion performance [message #43343 is a reply to message #43248]

Wed, 30 March 2005 07:21

Chris Lee
Messages: 101
Registered: August 2003

Senior Member

In article
<Pine.LNX.4.44.0503301010060.7505-100000@localhost.localdomain>, "Timm
Weitkamp" <dont.try@this.address> wrote:

> On 29.03.05 at 10:55 +0100, Ricardo Bugalho wrote:
>> I think I didn't make clear the ranges of m,n and p. In the problem I
>> have at hand, m is always 8, n is usually 5 (min 1, max 16) and p is in
>> the range of 10,000 to 100,000. Looping over p is a BadThing(tm) due to
>> IDL's high interpretation overhead.
> The method that Chris Lee suggested does not use loops. But I think
> there is no need for any call to REFORM. And the dimension arguments to
> REBIN must be scalars in IDL 5.4. A simple
>
> b = rebin(a, m, n, p, /sample)
> should therefore work (and, hopefully, be fast enough for your
> purposes). Timm
>

My first reaction was "when did that happen?", I tried it without the
reform, and it works...except

IDL> help, rebin(fltarr(4,5),[7,4,5,6])
% REBIN: Result dimensions must be integer factor of original dimensions

doesn't work (6.1.1 Linux), but the reform version does

IDL> help, rebin(reform(fltarr(4,5),[1,4,5,1]),[7,4,5,6])
<Expression> FLOAT = Array[7, 4, 5, 6]

So my world-view isn't completely shattered :)

Chris.

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[Message index]

		Re: Matrix expansion performance By: Timm Weitkamp on Wed, 30 March 2005 00:22
		Re: Matrix expansion performance By: Ricardo Bugalho on Tue, 29 March 2005 01:55
		Re: Matrix expansion performance By: Kenneth P. Bowman on Mon, 28 March 2005 05:50
		Re: Matrix expansion performance By: Chris Lee on Mon, 28 March 2005 05:43
		Re: Matrix expansion performance By: Chris Lee on Wed, 30 March 2005 07:21
		Re: Matrix expansion performance By: Ricardo Bugalho on Wed, 30 March 2005 04:18

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