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Re: image subtraction [message #29746 is a reply to message #11675]

Mon, 18 March 2002 21:45

Dick Jackson
Messages: 347
Registered: August 1998

Senior Member

"Kenneth Bowman" <k-bowman@null.tamu.edu> wrote in message
news:k-bowman-F0D133.10113317032002@news.tamu.edu...
> In article <MO3k8.1762$HJ.1430@shaw-ty1>,
> "Dick Jackson" <dick@d-jackson.com> wrote:
>
> What's the timing for
>
> imgarr = imgarr - rebin(reform(img1,512,512,1),512,512,12) ?

Good question. I don't know why it would be so, but it's longer:

>>>> > img1 = lonarr(512,512)
>>
>>>> > imgArr = lonarr(12,512,512)
>>
>> Using the methods suggested previously, this is likely to be faster (due
>> to better cache use) if you can dimension this array as
>>
>> imgArr = LONARR(512,512,12)
>
> Good thinking, Ken, if this is an option for Art.
> To round out the timings (YMMV):
>
> FOR ii=0,11 DO imgArr[ii,*,*] = imgArr[ii,*,*] - img1 : 1.402 s
>
> FOR ii=0,11 DO imgArr[ii,0,0] = imgArr[ii,*,*] - img1 : 1.232 s
>
> FOR ii=0,11 DO imgArr[*,*,ii] = imgArr[*,*,ii] - img1 : 0.741 s
>
> FOR ii=0,11 DO imgArr[0,0,ii] = imgArr[0,0,ii] - img1 : 0.301 s
>
> A big win there!
>
> For completeness:
> imgarr = imgarr - rebin(reform(img1,1,512,512),12,512,512) : 0.210 s

For even more completeness:

imgarr = imgarr - rebin(reform(img1,512,512,1),512,512,12) : 0.260 s

Again, this is on IDL 5.5, Win2000.

Cheers,
--
-Dick

Dick Jackson / dick@d-jackson.com
D-Jackson Software Consulting / http://www.d-jackson.com
Calgary, Alberta, Canada / +1-403-242-7398 / Fax: 241-7392

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[Message index]

		Image subtraction By: FRANCOIS LAROSE on Mon, 18 May 1998 00:00
		Re: Image subtraction By: noname on Tue, 26 May 1998 00:00
		Re: image subtraction By: Dick Jackson on Mon, 18 March 2002 21:45
		Re: image subtraction By: K. Bowman on Sun, 17 March 2002 08:11
		Re: image subtraction By: Dick Jackson on Thu, 14 March 2002 08:00
		Re: image subtraction By: Kenneth P. Bowman on Thu, 14 March 2002 04:55
		Re: image subtraction By: Dick Jackson on Wed, 13 March 2002 18:48
		Re: image subtraction By: Craig Markwardt on Wed, 13 March 2002 16:21

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