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[Support #KES-115113]: Existing convention for secondary GC-MS data

Hi John,

> P.S. NetCDF-4 sounds so cool, particularly the HDF5 aspect. I 
> imagine such files will be considerably quicker during
> acquisition. Is there a timetable for 4?

The timetable for netCDF-4 depends on when HDF5 version 1.8 is released.  The 
most recent estimate for that from the HDF Group is December, 2006.  We're 
guessing we can release netCDF-4 within a few weeks of that, if there are no 
unanticipated difficulties.  The current alpha release of netCDF-4 for internal 
testing is based on an alpha release of HDF5 1.8, and as a result the format 
has some artifacts we don't want to support in the real release.

> P.P.S. I'm accessing NetCDF.dll with the R package RNetCDF. I
> may be missing it, but I don't see a handle in RNetCDF by
> which to postpone filling during addition to the undefined
> dimension (and I'm not sure I'm clear on this option even if
> I were using the C or Fortran interface).  What is the
> command in the C software? I have two large arrays and some
> vectors with the undefined dimension. I'm guessing I'll boost
> efficiency by writing into the two arrays first, then the
> vectors (less filling).  What do you think?

In C, to change to "no fill" mode after you open a file for writing, but before 
you start writing, just call

  status = nc_set_fill(ncid, NC_NOFILL, &old_fill_mode);

where "old_fill_mode" is an integer into which the previous fill mode is 
returned, so you could restore the previous state if you wanted to.

By using no fill mode, you can reduce the I/O for writes by up to 50%, but you 
should only do this if you know you will write all the values. Otherwise if you 
read unwritten data values later, there will be no way to tell that they were 
not written.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: KES-115113
Department: Support netCDF
Priority: Normal
Status: Closed