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Re: simple vectorizing problem [message #62460 is a reply to message #62457]

Tue, 09 September 2008 01:50

Chris[6]
Messages: 84
Registered: July 2008

Member

Looks like the memory allocation overhead associated with
vectorization is worse than looping:

vectorization 1 time: 5.0360808 s
vectorization 2 time: 4.8453941 s
looping itme: 4.0875931 s

The vectorization performances become comparitvely worse as the array
grows (both reform() and total() create temporary, large arrays).

chris

pro test

nimage = 1500
im = fltarr(512,512,nimage)

t0 = systime(/seconds)
mean=total(reform(im,512L*512L, nimage), 1)/(512.*512)
t1=systime(/seconds)

mean=total(total(im,1),1)/(512.*512.)

t2 = systime(/seconds)

for i=0, nimage-1, 1 do $
mean[i]=total(im[*,*,i])/(512.*512)

t3=systime(/seconds)

print, t1-t0
print, t2-t1
print, t3-t2

end

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[Message index]

		Re: simple vectorizing problem By: David Fanning on Wed, 10 September 2008 17:14
		Re: simple vectorizing problem By: dpm314 on Wed, 10 September 2008 16:53
		Re: simple vectorizing problem By: Foldy Lajos on Tue, 09 September 2008 02:58
		Re: simple vectorizing problem By: Chris[6] on Tue, 09 September 2008 01:50
		Re: simple vectorizing problem By: David Fanning on Mon, 08 September 2008 19:17
		Re: simple vectorizing problem By: dpm314 on Mon, 08 September 2008 18:48
		Re: simple vectorizing problem By: JD Smith on Thu, 11 September 2008 11:56
		Re: simple vectorizing problem By: Spon on Thu, 11 September 2008 05:15

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