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Avoiding Loops in IDL 8.2.2 [message #85013]

Fri, 21 June 2013 17:04

Nate Tellis
Messages: 2
Registered: June 2013

Junior Member

Hi all,

I have a series of 711x4096x3 arrays. I am searching for good fits to a model, which is an 11x19 array, using a reduced chi-square fit. As it is now, I step across, pixel by pixel, column by column, pane by pane, and perform the fit to a subimage centred at the loop indices (normalized to the value of the central pixel). The fit is simple element-wise subtraction and squaring of the sub images, followed by one call to 'total' on the sub-image:

Chi^2_red = 1/Npixels * Sum over each pixel((image - fit)^2/error^2)

(This is of course fast, as the -, ^2, /, and 'total' operations utilize the IDL thread pool)

I know I can speed this up by using operations that leverage multithreading. How can I go about avoiding these hated nested for loops? Performing the fits on all ~8,500,000 subimages without multithreading takes way too long - about 90 seconds on average.

Thank you for the help,
Nate

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[Message index]

		Avoiding Loops in IDL 8.2.2 By: Nate Tellis on Fri, 21 June 2013 17:04
		Re: Avoiding Loops in IDL 8.2.2 By: Nate Tellis on Sun, 23 June 2013 15:24
		Re: Avoiding Loops in IDL 8.2.2 By: Moritz Fischer on Sun, 23 June 2013 22:05

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