[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: mmaped netcdf files

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: Re: mmaped netcdf files
  • Date: Thu, 10 Apr 1997 08:16:09 -0600
> From: Brad Asztalos <address@hidden>
> To: address@hidden
> Subject: mmaped netcdf files

Hi Brad,

> I wonder if to your knowledge anyone has
> made the netcdf package support mmaping the
> files for faster access?  If not I would
> like to try this and of course supply the
> code to you when it is done and tested.
> Can you see any problems that might be encountered
> with this approach?

Glenn Davis has suggested doing this and may even have tried some
experiments in implementing it this way.  I'm CC:ing him on this
reply in case he wants to respond also.

The major problem I see is portability.  There are Unix systems that
don't implement the mmap() interfaces (e.g. Ultrix), although it's in
the X/Open standards as of Issue 4, Volume 2.  But netCDF is also
supposed to work on VMS, OS/2, and Win32, which may not have equivalent
functionality.

If you wanted to implement this just as an optimization for those
systems that support mmap(), you should either use the netCDF-3.3a alpha
release, or wait until the general release of netCDF-3 later this
month, because we won't be supporting changes made to the netCDF-2.4.3
version after the release of netCDF-3.

--Russ

_____________________________________________________________________

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