Hi Oliver
Today is a national holiday. Here in Colorado,
we are expecting near record breaking tempertures
[forecast high temperature is 16C :-) ]
Hence, I do not expect people to be logging in today.
I will let NCL's graphics people answer about future
png plans.
Comment: the reason why reading the grib1 or grib2
via NCL can take some time is that NCL is making
the variables on the GRIB files conform to a netCDF
data model. The issue is that GRIB is a *record format*
NOT a *file format* like netCDF or HDF. A GRIB file
is just a collection of individual grib records. There
are no rules. The grib records can be in any random
order. So NCL must look at the *entire file*. On the
fly, it creates pointers to records, creates uniqu
look like a netCDF file's contents. Importing to this
common data model comes at a price .... time to organize.
So, I doubt it is the overhead involved with using
"convert" that is the problem. It is the file
organization overhead that causes the slowdown.
--- I have never used MetView. I speculate it reads 'just' the grib records necessary for the plots. A possible alternative to using ncl_convert2nc offline: Use wgrib to strip off the required records and then have NCL work on the selected subset. Something along the following: system('"wgrib -s grib_file | grep ":HGT:500 mb:" | wgrib -i -grib \ grib_file -o temporary_grib_file" ') f = addfile ("temporary_grib_file.grb", "r") x = f->HGT... [do whatever] system("/bin/rm -f temporary_grib_file.grb" See: ftp://ftp.cpc.ncep.noaa.gov/wd51we/wgrib/tricks.wgrib ---- As far as creating png via convert, my style is the following: pltDir = "./" pltType = "png" pltName = "mjo_spectra" pltConvert = "-density 96 -trim +repage" These could be done via NCL's Command Line Arguments if desired ;------------------------------------------------------------ ; PLOTS ;------------------------------------------------------------ if (pltType.eq."png") then pltTypeLocal = "ps" else pltTypeLocal = pltType end if pltPath = pltDir+pltName wks = gsn_open_wks(pltTypeLocal,pltPath) [plot(s)] if (pltType.eq."png") then if (.not.isvar("pltConvert")) then pltConvert = " " ; default end if system("convert "+pltConvert+" "+pltPath+".ps "+pltPath+".png") system("/bin/rm -f "+pltPath+".ps") end if ======================== Regards D Oliver.Fuhrer_at_meteoswiss.ch wrote: > Hi all, > > We are currently benchmarking NCL against MetView (from ECMWF). The goal > would be to use NCL operationally to produce plots of our model output. > Most of these products are produced in time-critical mode. > > Currently, there seem to be two bottlenecks that are slowing NCL down > considerably as compared to MetView. The first is the reading of our > model output in grib1 format. After offline conversion using > ncl_convert2nc to NetCDF format and execution of the same script simply > reading a couple of fields from a couple of files, the script runs 10x > faster. The second is the generation of raster graphics using NCL. A lot > of our plots are disseminated in PNG or GIF format. MetView can directly > write these formats whereas NCL writes a PS or PDF and the raster format > is produced using the "convert" utility. > > 1) I would be very much interested in future plans for NCL concerning > these two points. > > 2) Would a generation of NCGM and conversion using ctrans to a raster > format bring any gain in performance? > > Thanks and kind regards, > Oliver > > > ________________________________________ > > Oliver Fuhrer > Numerical Models > > Federal Departement of Home Affairs FDHA > Federal Office of Meteorology and Climatology MeteoSwiss > > Kraehbuehlstrasse 58, P.O. Box 514, CH-8044 Zurich, Switzerland > > Tel. +41 44 256 93 59 > Fax +41 44 256 92 78 > oliver.fuhrer_at_meteoswiss.ch > www.meteoswiss.ch - First-hand information > > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > ncl-talk mailing list > List instructions, subscriber options, unsubscribe: > http://mailman.ucar.edu/mailman/listinfo/ncl-talk _______________________________________________ ncl-talk mailing list List instructions, subscriber options, unsubscribe: http://mailman.ucar.edu/mailman/listinfo/ncl-talkReceived on Mon Jan 19 2009 - 09:18:32 MST
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