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List: grass-stats
Subject: [STATSGRASS] kriging - too long time
From: e.pebesma () geo ! uu ! nl (Edzer J ! Pebesma)
Date: 2007-11-14 16:58:17
Message-ID: 46DAA071.4040608 () geo ! uu ! nl
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That might be "explained" as follows: 8 to 400 is a factor 25, solving a
covariance matrix is an O(N^2) operation so would slow down by a factor
25*25 = 625. The remaining factor 6 (seconds to hours: 3600/625) should
be attributable to the load of finding the nearest 400 neighbours
instead of 8 nearest neighbours. I don't know that behaviour (a
bucket-PR quadtree search index is used), but am not surprised.
Best wishes,
--
Edzer
Carlos "Gu?no" Grohmann wrote:
> Tomas,
>
> nmax has a strong influence on kriging time. In some tests I've done,
> interpolation time for and area with 520 rows x 430 cols ranged from
> about 20 seconds for nmax=8 up to 20 HOURS for nmax =399.
>
> best
>
> Carlos
>
>
>
>
> On 9/2/07, Tomas Lanczos <lanczos@t-zones.sk> wrote:
>
>> I am performing some kriging following the procedure as it is here:
>> http://casoilresource.lawr.ucdavis.edu/drupal/node/438
>>
>> My problem is that the kriging proces is very slow, it takes approx. 7
>> hours. Is the problem a too high resolution, or too much sampling points
>> (2234)? How can I optimalize the process?
>>
>> My region setup is the following:
>>
>> projection: 1 (UTM)
>> zone: 33
>> datum: ** unknown (default: WGS84) **
>> ellipsoid: bessel
>> north: 5387295.0553002
>> south: 5288130.42061478
>> west: 652025.98376024
>> east: 786301.92841404
>> nsres: 150.02214022
>> ewres: 150.02898844
>> rows: 661
>> cols: 895
>> cells: 591595
>>
>> Many thanks
>>
>> Tomas
>>
>> _______________________________________________
>> statsgrass mailing list
>> statsgrass@grass.itc.it
>> http://grass.itc.it/mailman/listinfo/statsgrass
>>
>>
>
>
>
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