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Re: Search routines [message #12841 is a reply to message #12829]

Fri, 18 September 1998 00:00

landsman
Messages: 93
Registered: August 1991

Member

>
> I realize that WHERE will do the job, but at very low efficiency. WHERE
> makes no assumptions about the list being ordered. It seems to me it has
> to check every element of the array, requiring N steps for an N-element
> array. This is even worse than a linear search of an ordered list, which
> would require an average of N/2 steps. A simple bisection search would be
> LOG2(N) on average, which is, of course, very advantageous for large N.
>

The procedure tabinv.pro in http://idlastro.gsfc.nasa.gov/pub/ftp/math

will perform a vectorized binary search of a monotonic array.

Wayne Landsman landsman@mpb.gsfc.nasa.gov

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[Message index]

		Re: Search routines By: bowman on Fri, 18 September 1998 00:00
		Re: Search routines By: Liam Gumley on Fri, 18 September 1998 00:00
		Re: Search routines By: landsman on Fri, 18 September 1998 00:00
		Re: Search routines By: bowman on Fri, 18 September 1998 00:00
		Re: Search routines By: Alexander Proussevitc on Fri, 18 September 1998 00:00
		Re: Search routines By: davidf on Fri, 18 September 1998 00:00

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