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Re: Zero vector detection in IDL [message #16101 is a reply to message #16038]

Mon, 28 June 1999 00:00

Pavel Romashkin
Messages: 166
Registered: April 1999

Senior Member

Using WHERE does search through the entire array. I tried it: on my Power
Mac I could only get a FINDGEN(10,500,000) in memory, and locating randomly
incerted zeros in it using WHERE took 1.6 s. Unless your arrays are much
larger, I'd stick with WHERE for simplicity sake. Saves about 8 lines of
code, which I am not sure would speeds things up much: what if your
non-zero is at the end? You will loose an hour to loop through 10,500,000
elements.
Good luck,
Pavel

Frank Morgan wrote:

> Given a big byte or integer array (actually a 1-D vector), is there a
> fast IDL way to check whether any non-zero elements exist?
>
> Something like "if (total(x) EQ 0)..." or a where() construct will work,
> but scans the whole vector when the first non-zero element is enough to
> answer the question. max(x) is even worse.

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[Message index]

		Re: Zero vector detection in IDL By: J.D. Smith on Wed, 30 June 1999 00:00
		Re: Zero vector detection in IDL By: Pavel Romashkin on Mon, 28 June 1999 00:00

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