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Re: Vectorization question [message #21692]

Tue, 12 September 2000 12:34

promashkin
Messages: 169
Registered: December 1999

Senior Member

Hi Liam,
I came up with a different approach. For short arrays in a loop, it is 3
times slower than your method, Liam. However, with A being 1,000,000 and
both X and B 100,000 elements long, your method could not allocate
memory on my machine, while mine ran in 0.07 s. Check out the code
below. The loops were put in to get runtime extimates.
I run 5.3 on PowerMac G4, 192 MB total RAM, 64 MB allocated to IDL.
Cheers,
Pavel

pro pavel, a, b, x
out = a
start = systime(1)
;for i =0, 10000 do begin
ind = x[uniq(x, sort(x))]
loc = value_locate(x, ind)
sum_b = total(b, /cumulative)
res = [0, sum_b[loc], 0]
a_values = (res-shift(res, 1))[1:n_elements(res)-2]
out[ind] = a_values
;endfor
print, systime(1) - start
;print, out, format='(10i4)'
end

pro liam, a, b, x
out = a
start = systime(1)
;for i =0, 10000 do begin
tmp = intarr(n_elements(a), n_elements(x))
tmp[x, indgen(n_elements(x))] = b
out = a + total(tmp, 2)
;endfor
print, systime(1) - start
;print, out, format='(10i4)'
end

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[Message index]

		Re: Vectorization question By: promashkin on Tue, 12 September 2000 12:34
		Re: Vectorization question By: Liam E. Gumley on Mon, 11 September 2000 15:06
		Re: Vectorization question By: Craig Markwardt on Sun, 17 September 2000 00:00

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