[Met_help] More MET questions

[John Halley Gotway]

Dan,

Right now the answer is no.  There's no way of caching the polygon mask and reusing it.

One thing that would be pretty straightforward though would be to allow the user to specify the masking region as a bitmap directly (i.e. instead of a polyline).  We would probably want the bitmap to
be in NetCDF.  That would make parsing the masking region much faster since we'd just read it from a grid.

However, I'm still curious if that's really what's taking so long.  I wonder if it's actually the bootstrapping step that's slow... because when using many points, it's VERY slow.

Would you mind sending over the following sample data:
- the polyline mask
- the configuration file you're using (i.e. MODE or Grid-Stat or Point-Stat)
- a sample forecast file
- the matching observation file

Thanks,
John

John Halley Gotway wrote:
> Dan,
> 
> I'm headed out for the day right now, but I just wanted to point out one thing quickly.
> 
> Regarding GSL, please see the entry about GSL on the known issue page of the MET website:
> http://www.dtcenter.org/met/users/support/known_issues/METv1.1/index.php
> Look in the section on Grid-Stat.
> 
> And yes, it does seem like a very long time to be handling a mask.  I'll think more about that tomorrow and let you know.
> 
> John
> 
> 
> Daniel Schaffer wrote:
>> Hello John
>>
>> I've run into a couple of new issues with running MET that I thought you might have some ideas on.
>>
>> 1. We have chosen to run MET on data that is on the NCWD lat/lon grid.  When I run the grid_stat tool, I'm getting an error in one of the GSL libraries:
>>
>> gsl: gamma_inc.c:99: ERROR: error
>> Default GSL error handler invoked.
>>
>> It looks like some max iteration threshold is being exceeded in the gamma_inc_P_series subroutine.
>>
>> This error occurs even if the forecast and obs input files are identical.  I've attached the config file that I'm using and the header of the forecast netCDF file that I'm using.  I'm wondering if this error is occurring during calculation of the stats.  If so, is there any way to have MET just compute the dichotomous counts and thus bypass this error?  The counts are all that I need.
>>
>> 2. The other problem I'm having is that it is taking a very long time for MET to deal with the mask polygon that I have.  The polygon has O(3000) points.  Combine that with the large NCWD grid and it's taking about 20 minutes on my PC to finish handling the polygon (presumably generating bit masks).  Does that seem inordinately long to you?  If not, is there some way for me to cache the coresponding bit masks so that I don't have to pay this penalty every time I call MET (which will be hundreds or thousands of times)?
>>
>> Thanks,
>> Dan
>>
>> -------------------------------------------------------------------------------
>>
>> Dan Schaffer, Research Associate            e-mail: Daniel.S.Schaffer at noaa.gov
>> NOAA/OAR/Earth System Research Lab         phone:  (303) 497-7252
>> Aviation Branch                             fax:    (303) 497-6301
>> R/GSD5   325 Broadway                       
>> Boulder, CO 80305
>>
>> www-ad.fsl.noaa.gov/ac/schaffer.html
>>
>>
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>>
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