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better documentation for compact storage

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Edward Hartnett 2019-12-16 09:52:59 -07:00
parent fb4a209f2a
commit 19fef32a9e
1 changed files with 25 additions and 5 deletions
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libdispatch/dvar.c
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@ -452,9 +452,25 @@ nc_def_var_fletcher32(int ncid, int varid, int fletcher32)
/**
Define chunking parameters for a variable
The function nc_def_var_chunking sets the chunking parameters for a
variable in a netCDF-4 file. It can set the chunk sizes to get chunked
storage, or it can set the contiguous flag to get contiguous storage.
The function nc_def_var_chunking sets the storage and, optionally,
the chunking parameters for a variable in a netCDF-4 file.
The storage may be set to NC_CONTIGUOUS, NC_COMPACT, or NC_CHUNKED.
Contiguous storage means the variable is stored as one block of
data in the file.
Compact storage means the variable is stored in the header record
of the file. This can have large performance benefits on HPC system
running many processors. Compact storage is only available for
variables whose data are 64 KB or less. Attempting to turn on
compact storage for a variable that is too large will result in the
::NC_EVARSIZE error.
Chunked storage means the data are stored as chunks, of
user-configurable size. Chunked storage is required for variable
with one or more unlimted dimensions, or variable which use
compression.
The total size of a chunk must be less than 4 GiB. That is, the
product of all chunksizes and the size of the data (or the size of
@ -467,8 +483,8 @@ nc_def_var_fletcher32(int ncid, int varid, int fletcher32)
Note that this does not work for scalar variables. Only non-scalar
variables can have chunking.
@param ncid NetCDF ID, from a previous call to nc_open or
nc_create.
@param ncid NetCDF ID, from a previous call to nc_open() or
nc_create().
@param varid Variable ID.
@ -501,6 +517,10 @@ nc_def_var_fletcher32(int ncid, int varid, int fletcher32)
@return ::NC_EBADCHUNK Returns if the chunk size specified for a
variable is larger than the length of the dimensions associated with
variable.
@return ::NC_EVARSIZE Compact storage attempted for variable bigger
than 64 KB.
@return ::NC_EINVAL Attempt to set contiguous or compact storage
for var with one or more unlimited dimensions.
@section nc_def_var_chunking_example Example