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Re: Cyclic array interfaces [message #40187]

Tue, 13 July 2004 19:53

Mark Hadfield
Messages: 783
Registered: May 1995

Senior Member

Cedric wrote:
> Mark Hadfield <m.hadfield@niwa.co.nz> wrote in message news:<cd1no6$q54$1@newsreader.mailgate.org>...
>
>> Analysis be dammed, I counted them! And got a result that disagrees with
>> your analysis:
>
>
> :) I should have remembered that programmers are always wrong when
> they don't use a profiler!
>
> I'm still surprised by your result, though. Perhaps IDL knows that
> findgen(n) is a temporary in the first case (thus assigning its
> address directly to a) and not in the second case.

The result below supports this.

> I don't have access
> to IDL now, but I would try
>
> n = 10000000 & a = fltarr(n) & b = findgen(n) & t0 = systime(1) & a =
> b & t1 = systime(1) & a[0] = b & t2 = systime(1) & print, t1-t0, t2-t1

0.14100003 0.093999863

The results are pretty consistent, by the way.

--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)

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[Message index]

		Re: Cyclic array interfaces By: Mark Hadfield on Tue, 13 July 2004 19:53
		Re: Cyclic array interfaces By: cedricl on Tue, 13 July 2004 18:48
		Re: Cyclic array interfaces By: Mark Hadfield on Tue, 13 July 2004 15:29
		Re: Cyclic array interfaces By: cedricl on Tue, 13 July 2004 05:59
		Re: Cyclic array interfaces By: David Fanning on Mon, 12 July 2004 17:50

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