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Re: avoiding for loop when calculating median [message #10937 is a reply to message #10936]

Mon, 02 February 1998 00:00

George McCabe
Messages: 23
Registered: June 1997

Junior Member

Thanks for your inputs, Alex.

following an earlier hint on the group I wrote the loop like you
describe, but without REFORM'ing the matrix. To be honest my matrix is
a large data cube, but I chose a 2D example to make the description less
opaque. The reduction in execution time was measured - 20%, which on 45
seconds is significant. When you say HUGE is that the scale of the
increase you experienced.

I didn't REFORM the data because I figured it wasn't worth the extra
step as the cube can be addressed directly as 1D. But if yours ran much
faster including the step to REFORMAT then I'll try it.

Thanks again, George

Alex Schuster wrote:
>
> Oops! I wrote:
>
>> I assume that mat is an idim x jdim array. mat(cnt,*) gives the elements
>> no. cnt, cnth+idim, cnth+2*idim etc., I guess it's easier to use
>> mat2=reform(mat), so all the elements are in line.
>
> Don't know why I wrote REFORM here, it's TRANSPOSE.
> I just tested this with an 5000x5000 float array, there is a HUGE
> difference in the execution time.
>
> Alex

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George McCabe (HSTX) NASA / GSFC
Tel: (301)286-8283, Fax: (301)286-0212 Code 693, B2 R151
E-mail: george.mccabe@gsfc.nasa.gov Greenbelt, MD 20912

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[Message index]

		Re: avoiding for loop when calculating median By: Alex Schuster on Mon, 02 February 1998 00:00
		Re: avoiding for loop when calculating median By: George McCabe on Mon, 02 February 1998 00:00
		Re: avoiding for loop when calculating median By: Alex Schuster on Fri, 30 January 1998 00:00
		Re: avoiding for loop when calculating median By: George McCabe on Fri, 30 January 1998 00:00
		Re: avoiding for loop when calculating median By: a2652099 on Fri, 30 January 1998 00:00
		Re: avoiding for loop when calculating median By: Michael Werger on Fri, 30 January 1998 00:00

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