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Re: 20001017: question

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  • Subject: Re: 20001017: question
  • Date: Tue, 17 Oct 2000 15:29:41 -0600
>To: "'address@hidden'" <address@hidden>
>From: "Krussel, Michael" <address@hidden>
>Subject: question
>Organization: Harris
>Keywords: 200010171856.e9HIuk400090

Hi Michael,

> In the foreword for NetCDF User's Guide for C, it says, "However, the netCDF
> library also allows direct-access storage and retrieval of data by variable 
> name
> and index and therefore is useful only for disk-resident (or memory-resident)
> datasets.  How would you use the netCDF functions on a memory-resident 
> dataset.

Although I didn't write the foreward, I think Dave Fulker just meant
that netCDF relies on the lseek() call to access data directly
(randomly) by offset rather than sequentially, so it is not very
useful for accessing data from a tape, for example.  

There is an experimental implementation of netCDF that memory-maps
files using the Unix mmap() call and then treats the data as if it's
all contained in a big in-memory array.  For more details on the mmap
implementation, see:

  http://www.unidata.ucar.edu/glimpse/netcdfgroup-list/1119

--Russ

_____________________________________________________________________

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