| Re: Convolution of Stick Spectra [message #21768 is a reply to message #21721] |
Thu, 14 September 2000 00:00  |
mole6e23
Messages: 31
Registered: December 1998
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Member |
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bjackel@phys.ucalgary.ca wrote:
> It helps a bit to pre-calculate your variance term.
> Cuts execution time from 27 to 18 seconds on my PC.
>
> variance_term= ( ( (.12*sqrt(energy/1000))/1.6651)*1000)^2
> FOR indx=0L,nstick-1 DO BEGIN
> result = result + intensity[indx]* $
> exp(-((energy_scale - energy[indx])^2)/
> variance_term[indx] )
> ENDFOR
>
Actually, I was surprised to find that didn't change the timing any on my
sytem (alpha OSF unix 5.3 Nov 11 1999) to any appreciable degree. With the
code I first posted (attached below as a procedure), it took about 10.5
seconds either way.
IDL> test
time other: 10.706325
time precalc: 10.545039
Jumping up to 20,000 elements, the timing was still pretty much identical
(42.9 vs. 42.7 seconds).
Todd
----
pro test
convoluted = fltarr( 2, 2048 )
convoluted[0,*] = findgen( 2048 ) / 2047. * 4.
;; Let's fake a stick spectrum, we usually have at least this many elements
stick = abs(randomn( systime(1), 2, 5000 ))
stick[0,*] = stick[0,*] * 4.
stick[1,*] = stick[1,*] * 1000.
time = systime(1)
variance = (((.12*sqrt(stick[0,*]/1000))/1.6651)*1000)^2
for i=0L, n_elements( stick ) / 2 -1 do $
convoluted[1,*] = stick[1,i]*exp(-((convoluted[0,*] - stick[0,i])^2)/ $
variance[i]) $
+ convoluted[1,*]
time2 = systime(1)
for i=0L, n_elements( stick ) / 2 -1 do $
convoluted[1,*] = stick[1,i]*exp(-((convoluted[0,*] - stick[0,i])^2)/ $
(((.12*sqrt(stick[0,i]/1000))/1.6651)*1000)^2) $
+ convoluted[1,*]
print, 'time other: ', systime(1) - time2
print, 'time precalc: ', time2 - time
end
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