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Re: Sort without loops [message #45165 is a reply to message #45162]

Wed, 17 August 2005 03:36

peter.albert@gmx.de is currently offline

peter.albert@gmx.de
Messages: 108
Registered: July 2005

Senior Member

Hi Ian,

> Is there a clever way of sorting on two fields like this without using a
> loop. The above algorithm is faaaar slower than just using sort.

I don't know how to sort over two fields at the same time, but I could
propose a much faster way ofcreating you new string array, avoiding the
for loop:

spos = strpos(array, ";")

left = strmid($
array, $
transpose(replicate(0, n_elements(array))), $
transpose(spos)$
)

right = string($
fix($
strmid($
array, $
transpose(spos+1)),$
), $
format = '(i4.4)'$
)

The basic idea is to use an array for the variables "first_character"
and "length" in the call to strmid. It has to be the transposed ones,
as the first dimension of those arrays determines how many substrings
are extracted from each element of the string array - one in your case.

On my PC this method is approx. 10 times faster as the for-loop. If it
is still too slow, one could think of providing more sophisticated
arrays for first_character and length with a 2 as first dimension, i.e.
extracting both substrings in one go. But I doubt that this would
really help a lot.

Best regards,

Peter

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[Message index]

		Re: Sort without loops By: JD Smith on Wed, 17 August 2005 12:02
		Re: Sort without loops By: R.Bauer on Wed, 17 August 2005 07:24
		Re: Sort without loops By: peter.albert@gmx.de on Wed, 17 August 2005 03:36

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