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Re: find max in 3D array -- slow [message #70457 is a reply to message #70378]

Mon, 12 April 2010 10:48

JDS
Messages: 94
Registered: March 2009

Member

On Apr 10, 12:03 pm, "Timothy W. Hilton" <hil...@meteo.psu.edu> wrote:
> Hello IDL users,
>
> I have a 1200x1200x2900 array of floats. The dimensions correspond to
> latitude x longitude x time. I need to find the maxium at each
> location -- that is, I need the 1200x1200 array containing the max
> along the 3rd dimsion. IDL takes almost 3 minutes to do this on my
> system. This seemed slow. I compared it with Matlab, which took ten
> seconds. Is there a better way to search for the maxima using IDL?

It would be of interest to run your IDL vs. MATLAB test again with an
array size which can easily fit in memory (e.g. 500MB worth). I'd
guess that most of that 3 minutes is spent hitting the disk for page
faults. The data ordering of IDL vs. MATLAB could easily come into
play, though both are column-major. I get about 1s for 500MB, which
should scale to ~30s for your data set (and I'll guess your machine is
faster than mine).

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[Message index]

		find max in 3D array -- slow By: Timothy W. Hilton on Sat, 10 April 2010 09:03
		Re: find max in 3D array -- slow By: JDS on Mon, 12 April 2010 10:48
		Re: find max in 3D array -- slow By: Juggernaut on Mon, 12 April 2010 09:20
		Re: find max in 3D array -- slow By: Steve[5] on Mon, 12 April 2010 04:15
		Re: find max in 3D array -- slow By: Maxwell Peck on Mon, 12 April 2010 03:36

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