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Re: FOR loops removal [message #62116 is a reply to message #61975]

Thu, 21 August 2008 11:34

Chris[6]
Messages: 84
Registered: July 2008

Member

What about something like this?

s= 2*(array le 2)-1
array = (array ne 0)*array + (array eq 0)*(shift(s,1)+shift(s,-1))

You'll have to manually fix the endpoints, but the rest should be
good. I tested this and the first loop on an array of 400,000
elements. The first loop rand in .54 seconds, while the second ran in .
054s.

Also, you should be a little careful when testing whether array equals
zero. If the array isn't an integer type (int, byte, long, etc), then
its possible to have numbers you think ought to be zero but, because
of finite precision arithmetic, have very small nonzero values. If you
suspect that this is happening, you can try a test like abs(array) le
eps, where eps is something like 10^-5 or something big enough to
cover roundoff error but small enough not to treat nonzero data you
care about as zero

chris

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[Message index]

		FOR loops removal By: loebasboy on Tue, 19 August 2008 05:38
		Re: FOR loops removal By: loebasboy on Thu, 21 August 2008 07:27
		Re: FOR loops removal By: Jeremy Bailin on Thu, 21 August 2008 08:40
		Re: FOR loops removal By: Jeremy Bailin on Thu, 21 August 2008 06:39
		Re: FOR loops removal By: loebasboy on Thu, 21 August 2008 00:59
		Re: FOR loops removal By: Jeremy Bailin on Wed, 20 August 2008 07:07
		Re: FOR loops removal By: loebasboy on Wed, 20 August 2008 05:36
		Re: FOR loops removal By: David Fanning on Tue, 19 August 2008 13:14
		Re: FOR loops removal By: loebasboy on Mon, 25 August 2008 01:31
		Re: FOR loops removal By: Chris[6] on Fri, 22 August 2008 11:19
		Re: FOR loops removal By: ben.bighair on Fri, 22 August 2008 03:50
		Re: FOR loops removal By: loebasboy on Fri, 22 August 2008 02:08
		Re: FOR loops removal By: Chris[6] on Thu, 21 August 2008 11:34

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