Dennis,
It doesn't look like there is a version 4.2.1.1, at least not for the
NetCDF-4 C++ libraries, according to this:
http://www.unidata.ucar.edu/downloads/netcdf/netcdf-cxx/index.jsp
It hasn't been updated since I installed it over a month ago.
Taylor
On Tue, Feb 19, 2013 at 2:20 PM, Taylor Binnington <tbinnington@xxxxxxxxx>wrote:
> Thank you both.
>
> First, in reply to Christopher's suggestion:
>
> I've explored the documentation
> here<http://www.unidata.ucar.edu/software/netcdf/docs/cxx4/index.html> as
> well as the
> test_var.cpp<http://www.unidata.ucar.edu/software/netcdf/docs/cxx4/test_var_8cpp-example.html#_a10>
> example
> program, in addition to a few other sources. I'm finding the documentation
> quite opaque, regarding learning to extract only certain indices or an
> array via the NetCDF API. However, one thing I've gleaned is that
> subsetting parameters are specified as a NetCDF Group; however, this data
> structure is not found in MERRA files, since Groups are only supported by
> NetCDF-4 files.
>
> Second, in reply to Dennis' request. The output from
>
> ncdump '[log][show=fetch]
> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf?U50M_EOSGRID_Data_Fields[0:23][282:282][441:441]
> '
>
> is the following:
>
> Log:fetch:
> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf.dds
>
> Log:fetch complete: 2.906 secs
> Log:fetch:
> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf.das
>
> Log:fetch complete: 0.443 secs
> Log:fetch:
> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf.dds?U50M_EOSGRID_Data_Fields[0:23][282][441]
>
> Log:fetch complete: 0.228 secs
> Log:prefetch: U50M_EOSGRID_Data_Fields=24
> Log:prefetch: U50M_EOSGRID_Data_Fields
> Log:prefetch.final:
> U50M_EOSGRID_Data_Fields*[0:23/24][0:360/361][0:539/540]
> Log:fetch:
> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf.dods?U50M_EOSGRID_Data_Fields
>
> Log:fetch complete: 58.994 secs
> Log:prefetch.complete
> Log:prefetch.vars: U50M_EOSGRID_Data_Fields
>
> netcdf MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101 {
> dimensions:
> TIME_EOSGRID = 24 ;
> XDim_EOSGRID = 1 ;
> YDim_EOSGRID = 1 ;
> variables:
> float U50M_EOSGRID_Data_Fields(TIME_EOSGRID, YDim_EOSGRID,
> XDim_EOSGRID) ;
> U50M_EOSGRID_Data_Fields:_FillValue = 1.e+15f ;
> U50M_EOSGRID_Data_Fields:long_name = "Eastward wind at 50
> m above surface" ;
> U50M_EOSGRID_Data_Fields:standard_name =
> "eastward_wind_at_50_meters" ;
> U50M_EOSGRID_Data_Fields:units = "m/s" ;
> U50M_EOSGRID_Data_Fields:scale_factor = 1.f ;
> U50M_EOSGRID_Data_Fields:add_offset = 0.f ;
> U50M_EOSGRID_Data_Fields:missing_value = 1.e+15f ;
> U50M_EOSGRID_Data_Fields:fmissing_value = 1.e+15f ;
> U50M_EOSGRID_Data_Fields:vmin = -1.e+30f ;
> U50M_EOSGRID_Data_Fields:vmax = 1.e+30f ;
> U50M_EOSGRID_Data_Fields:valid_range = -1.e+30f, 1.e+30f ;
> U50M_EOSGRID_Data_Fields:coordinates = "TIME_EOSGRID
> YDim_EOSGRID XDim_EOSGRID" ;
>
> // global attributes:
> :HDFEOSVersion = "HDFEOS_V2.14" ;
> :missing_value = 1.e+15f ;
> :Conventions = "CF-1.0" ;
> :title = "MERRA reanalysis. GEOS-5.2.0" ;
> :history = "File written by CFIO" ;
> :institution = "Global Modeling and Assimilation Office,
> NASA Goddard Space Flight Center, Greenbelt, MD 20771" ;
> :source = "Global Modeling and Assimilation Office.
> GEOSops_5_2_0" ;
> :references = "http://gmao.gsfc.nasa.gov/research/merra/";
> ;
> :comment = "GEOS-5.2.0" ;
> :contact = "http://gmao.gsfc.nasa.gov/"; ;
> data:
>
> U50M_EOSGRID_Data_Fields =
> 5.483779,
> 4.986389,
> 4.076741,
> 3.479807,
> 3.125561,
> 2.818876,
> 2.536896,
> 2.388737,
> 2.501732,
> 2.531001,
> 2.440533,
> 2.245501,
> 1.99101,
> 1.798543,
> 1.793866,
> 1.694912,
> 1.561274,
> 1.471124,
> 1.408249,
> 1.449105,
> 1.588835,
> 1.835351,
> 2.13877,
> 2.48236 ;
> }
>
>
>
> On Tue, Feb 19, 2013 at 11:00 AM, Lynnes, Christopher S. (GSFC-6102) <
> christopher.s.lynnes@xxxxxxxx> wrote:
>
>> On Feb 19, 2013, at 10:48 AM, Taylor Binnington <tbinnington@xxxxxxxxx>
>> wrote:
>>
>> > Thank you Dennis.
>> > I'm using version 4.2.1, netcdf-cxx4 by Lynton Appel, on openSUSE 12.1,
>> so I think it's fairly up-to-date. The problem is not that I am unable to
>> open the file (I, too, can print out the 24 values), but that doing so
>> apparently uses ~19 mb of bandwidth, according to the iftop monitoring
>> utility. This seems quite excessive.
>> > Please let me know if there is specific information that I should
>> provide here. Much appreciated,
>> > Taylor
>>
>> Taylor,
>> I think Benno might have put his finger on the issue over on the
>> opendap-tech mailing list. That is, instead of passing the fully
>> constrained URL to a read function, open the URL without the constraints
>> and then use one of the methods that allows you to specify the start and
>> length (or corner points) of the segment you want to retrieve. I know they
>> must be there somewhere, because the C API certainly has it.
>> >
>> >
>> > On Mon, Feb 18, 2013 at 5:57 PM, Dennis Heimbigner <
>> dmh@xxxxxxxxxxxxxxxx> wrote:
>> >
>> > The opendap code in the netcdf-C libraries
>> > (used by the C++ library) will in fact
>> > properly handle the constraint you specified.
>> > I just ran it and as expected, it is only pulling
>> > in the 24 values you requested (took some 5 seconds to
>> > obtain and print out the data).
>> >
>> > One possibility is that you are using a rather old version
>> > of the netcdf-C library.
>> >
>> > =Dennis Heimbigner
>> > Unidata
>> >
>> > Taylor Binnington wrote:
>> > Hello,
>> >
>> > I have an 'understanding' type of question. I have omitted details of my
>> > OS, NetCDF installation, and a minimal example since I do not think they
>> > are important for my question, but I can provide these details if they
>> are
>> > important.
>> >
>> > When I attempt to open a MERRA file using the NetCDF C++ libraries,
>> with a
>> > line like the following, in my code:
>> >
>> > NcFile datafile("
>> >
>> http://goldsmr2.sci.gsfc.nasa.gov/opendap/hyrax/MERRA/MAT1NXSLV.5.2.0/1990/01/MERRA100.prod.assim.tavg1_2d_slv_Nx.19900101.hdf?U50M_EOSGRID_Data_Fields[0:23][282:282][441:441]
>> > ",NcFile::read);
>> >
>> > ...I notice that quite a lot (nearly 20 MB) is being transferred from
>> Hyrax
>> > to my PC. However, all that I am interested in are the actual array
>> values
>> > (24 separate 32-bit real numbers) of the U50M_EOSGRID_Data_Fields. It
>> has
>> > been suggested that the entire array (of size 24*361*540 32-bit reals)
>> is
>> > being transferred by NetCDF before any subsetting takes place, is this
>> > true? If so, is it then not possible to use OPeNDAP URLs to subset
>> > on-the-fly through the NetCDF libraries?
>> >
>> > Thank you for your help!
>> > Taylor
>> >
>> >
>> >
>> > ------------------------------------------------------------------------
>> >
>> > _______________________________________________
>> > netcdfgroup mailing list
>> > netcdfgroup@xxxxxxxxxxxxxxxx
>> > For list information or to unsubscribe, visit:
>> http://www.unidata.ucar.edu/mailing_lists/
>> >
>> >
>> >
>> > --
>> > Taylor Binnington
>> > e. tbinnington@xxxxxxxxx
>> > c. 647 926 4144
>> > _______________________________________________
>> > netcdfgroup mailing list
>> > netcdfgroup@xxxxxxxxxxxxxxxx
>> > For list information or to unsubscribe, visit:
>> http://www.unidata.ucar.edu/mailing_lists/
>>
>> --
>> Dr. Christopher Lynnes, NASA/GSFC, ph: 301-614-5185
>>
>>
>>
>>
>
>
> --
> Taylor Binnington
> e. tbinnington@xxxxxxxxx
> c. 647 926 4144
>
--
Taylor Binnington
e. tbinnington@xxxxxxxxx
c. 647 926 4144
