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Re: Philosophy of for loops [message #21486]

Tue, 29 August 2000 00:00

landsman
Messages: 93
Registered: August 1991

Member

Todd Clements wrote:
>>
>> Hello, again, everyone!
>>
>> I was just wondering what the general concensus of the "IDL Expert
>> Programmers" was on the use of for loops. When I first learned IDL,

A related question is when is it better to write loops as a single line,
and when is it better to use a DO BEGIN construct. For example,

inarr= randomn(seed, 3, 2048,2048)
outarr = fltarr(2048,2048,/nozero)

(1) for j=0,2047 do for i=0,2047 do outarr[i,j] = median(inarr[*,i,j])

(2) for j=0,2047 do begin
for i=0,2047 do begin
outarr[i,j] = median(inarr[*,i,j])
endfor
endfor

Form (1) is slightly faster, but the calculation cannot be interrupted
with a Control-C. Also, it is my impression that the speed difference
is less than it used to be, and that form (2) is now better optimized.

(I also assume that the two FOR loops are unavoidable here, but I would
be delighted to be proved wrong.)

--Wayne Landsman landsman@mpb.gsfc.nasa.gov

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[Message index]

		Re: Philosophy of for loops By: landsman on Tue, 29 August 2000 00:00
		Re: Philosophy of for loops By: davidf on Tue, 29 August 2000 00:00
		Re: Philosophy of for loops By: Nando Iavarone on Tue, 29 August 2000 00:00
		Re: Philosophy of for loops By: Martin Schultz on Tue, 29 August 2000 00:00
		Re: Philosophy of for loops By: marc schellens[1] on Mon, 28 August 2000 23:43
		Re: Philosophy of for loops By: John-David T. Smith on Mon, 28 August 2000 22:14
		Re: Philosophy of for loops By: Craig Markwardt on Mon, 28 August 2000 00:00

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