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Re: How to speed up or remove this FOR loop [message #74535 is a reply to message #74453]

Fri, 21 January 2011 08:02

wlandsman
Messages: 743
Registered: June 2000

Senior Member

On Friday, January 14, 2011 4:00:25 AM UTC-5, johan wrote:
> I do have 768 profiles, each 24 pixels long, each to whom I want to
> fit a Gaussain and getting the mean and SD. I am using the following
> FOR loop calling mpfitexpr. It works fine but it takes forever to
> complete!
>
> expr = 'P[0] + GAUSS1(X, P[1:3])'
>
> t = indgen(24)
> start = [20.D, 10, 2., 1000.]
>
> for i=0,(size(profiles,/dim))[1]-1 do begin
> r = profiles[*,i]
> result = mpfitexpr(expr, t, r, 1, start, /QUIET)
> endfor
>
Before I had suggested using MPFITFUN instead of MPFITEXPR, which should provide a modest speedup since one doesn't need an indirect function evaluation. Now I am going to suggest not to use the MPFIT* routines at all, but to instead use the ITTVIS supplied GAUSSFIT(). The MPFIT* routines are more robust, with more checking for overflows, NANs and more user diagnostics, but for simple Gaussian fits the overhead for GAUSSFIT() is *much* lower. (A factor of 4 speedup is possible.) --Wayne

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[Message index]

		How to speed up or remove this FOR loop By: johan[1] on Fri, 14 January 2011 01:00
		Re: How to speed up or remove this FOR loop By: wlandsman on Fri, 21 January 2011 08:02
		Re: How to speed up or remove this FOR loop By: johan[1] on Tue, 25 January 2011 16:12

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