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Re: Can I do this without using loops? [message #6301]

Sat, 08 June 1996 00:00

bowman
Messages: 121
Registered: September 1991

Senior Member

In article <4pcm41$64r@vixen.cso.uiuc.edu>, santanu@glibm5.cen.uiuc.edu (S
Bhattacharyya) wrote:

> Regarding loops, I am kinda in the same boat. My advisor
> keeps complaining about how slow our code runs...We don't seem to
> know any better around here :-)
>
> Q1) I have a generic array foo(x,y). I'd like to divide each column
> by its max. Can this be done without looping ?
>
> Q2) I have a generic array foo=fltarr(a,b). I'd like to copy findgen(b)
> into every column. Any way of doing this without loops ?

It is always the *innermost* loop that you need to worry about. Of course
you want to avoid taking large strides in memory in the innermost loop, as
well as using array syntax. A2 (below) should run very fast. I'm using
the first quadrant convention for subscripts (i.e., (i,j) corresponds to
(x,y), so to me a column is the second subscript. You may need to reverse
that.

A1)

FOR i = 0, ni-1 DO foo(i,*) = foo(i,*)/MAX(foo(i,*))

A2)

FOR j = 0, nj-1 DO foo(*,j) = FLOAT(j)

Regards, Ken Bowman

--
Kenneth P. Bowman, Assoc. Prof. 409-862-4060
Department of Meteorology 409-862-4132 fax
Texas A&M University bowman@csrp.tamu.edu
College Station, TX 77843-3150
Satellite ozone movies on CD-ROM --> http://www.lenticular.com/

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[Message index]

		Re: Can I do this without using loops? By: bowman on Sat, 08 June 1996 00:00
		Re: Can I do this without using loops? By: santanu on Sat, 08 June 1996 00:00
		Re: Can I do this without using loops? By: Bruce E Thomason on Thu, 06 June 1996 00:00
		Re: Can I do this without using loops? By: rivers on Wed, 05 June 1996 00:00
		Re: Can I do this without using loops? By: peter on Wed, 05 June 1996 00:00

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