[GRASS-user] Parallel GRASS jobs .....

[Andranik Hayrapetyan]

I think I don't understand the concept of region itself. Here is the output
of my g.region -p
projection: 0 (x,y)
zone:       0
north:      4569989.25
south:      4357350.75
west:       436605.75
east:       670334.25
nsres:      28.5
ewres:      28.5
rows:       7461
cols:       8201
cells:      61187661

Please, can you tell me how to reduce this region into 2 chunks.

Thanks in advance



On Wed, Nov 28, 2012 at 2:43 PM, Sylvain Maillard <
sylvain.maillard at gmail.com> wrote:

> > I was trying to do that with g.region, but it only resized my map and
> didn't "cut" it.
> In fact it didn't modify your map, but resize the area where the
> calculation is done byt hte other modules : with a small region defined in
> a mapset, your code will work only on that part of the map in the PERMANENT
> mapset.
>
> as an example with a region of n=100 s=0 e=100 w=0, you can pass the
> region limits to your script (eg: my_script.sh 50 0 50 0;  my_script.sh 100
> 50 50 0; ...) so the calculation are made only of a quarter of the whole
> region.
> if your script can handle arguments, it will the first define its own
> sub-region from what you passed to it: "g.region n=$1 s=$2 e=$3 w=$4"
>
> Sylvain
>
>
> 2012/11/28 Daniel Lee <lee at isi-solutions.org>
>
>> Hi there,
>>
>> I do this too and the standard methodology for me is to leave the
>> resolution the same and change the region's borders. Take a look at the
>> manual of g.region for guides on this, but let's say I've got the following:
>>
>> GRASS 6.4.3svn (EPSG4326_WGS84_ll):~ > g.region -g
>> n=63
>> s=-63
>> w=95
>> e=180
>> nsres=1.10020395685734e-05
>> ewres=1.10020399076346e-05
>> rows=11452422
>> cols=7725840
>> cells=88479579984480
>>
>> Then to reduce the region's size I'd do e.g.:
>> g.region n=50 s=-50 w=100 e=110
>>
>> That would "shrink" my region down to the area that I'm interested in.
>>
>> HTH!
>> Daniel
>>
>>
>>
>> 2012/11/28 Andranik Hayrapetyan <andranik.h89 at gmail.com>
>>
>>> I have been trying something like this some time ago, but I could not
>>> define region of a mapset as chunk of the whole region.
>>> Is g.region the right tool for this task?
>>> If it is not difficult for you, can you, please, explain the process of
>>>  doing  " *define the region of each mapset as a chunk of the whole
>>> region* " a bit more detailed.
>>>
>>>
>>> On Wed, Nov 28, 2012 at 1:56 PM, Sylvain Maillard <
>>> sylvain.maillard at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> for this approach, the best would be to
>>>> (before the multi-process job)
>>>> - put your map into the PERMANENT mapset
>>>>
>>>> (for each process in parallel)
>>>> - make a new mapset for each process
>>>> - define the region of each mapset as a chunk of the whole region
>>>> - make your calculation
>>>>
>>>> (once the process competed)
>>>> - put together all the results (eg, with r.patch)
>>>>
>>>>
>>>> Sylvain
>>>>
>>>>
>>>>
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>>>>
>>>>
>>>
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>>>
>>
>
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