NetCDF 3'6: Whats New

1
NetCDF 3.6 Whats New

• Russ Rew
• Unidata Program Center
• University Corporation for Atmospheric Research
• 2004-09-01

www.unidata.ucar.edu/packages/netcdf/
2
Overview

• A new format variant
• Backward compatibility
• Refactored documentation
• File size limitations eliminated
• Better configuration support
• Better Windows support
• Bug fixes, performance enhancements

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Larger netCDF files, 64-bit file offsets

• Current classic format uses 32-bit offsets
• New 64-bit offset format mode available on
  creation, for very large files
• nc_create(file, NC_64BIT_OFFSET, ncid)
• Initial development by Greg Sjaardema, Sandia
  Labs
• We added
• Fortran, C, ncgen, ncdump support
• Extensive additional error checking
• 2GiB to 4GiB variable size increase
• Elimination of 4GiB record size limit

4
Backward Compatibility

• Version 3.6 library reads classic format or new
  format transparently
• By default, new files are created in classic
  format
• New format should only be used for files too
  large for classic format
• No code changes needed for existing code
• Third-party software eventually should be
  upgraded to 3.6 to support new format

5
Refactored Documentation

• Users Guides for C, FORTRAN-77, FORTRAN-90
  converted from FrameMaker (proprietary) to
  Texinfo (GNU documentation system)
• Language-neutral Users Guide documents data
  model and language-independent concepts
• Language-specific guides for C, Fortran-77,
  Fortran-90, and C interfaces
• Will support better maintenance of documentation,
  easier addition of other language-specific manuals

6
Elimination of some size limitations
I GiB 230 or about 1.07 109 bytes
I EiB 260 or about 1.15 1018 bytes
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Better configuration support

• Upgraded to use latest autoconf configuration
  tool
• Builds with Large File Support by default, if
  available
• Tested on more platforms with more development
  environments

8
Better Windows support

• Included with source distribution in win32
  directory
• Added .Net port
• Builds with VC.NET from source
• Added windows installer files to build windows
  binary installs

9
Performance enhancements, bug fixes

• Fortran -77 implementation upgraded with more
  recent cfortran.h
• Added -x option to ncgen to use fast no fill
  mode for netcdf file creation
• Fixed ncdump and ncgen to properly handle
  dimension lengths gt 231
• Added new error codes for invalid dimension and
  variable size
• Added tests for invalid offsets in classic format
• Added performance fix for Fortran-90 array access
  interfaces