[netcdfgroup] nc_put_varm

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: [netcdfgroup] nc_put_varm
• From: Wei-keng Liao <wkliao@xxxxxxxxxxxxxxxxxxxxx>
• Date: Tue, 22 Apr 2014 12:31:55 -0500

My question is about how to set imapp argument in nc_put_varm().

At first the description of nc_put_varm() in C interface guide is inconsistent 
with the
document generated by doxygen.

In C interface guide, it says "nc_put_varm() function will write a variable of 
any type,
including user defined type"
http://www.unidata.ucar.edu/software/netcdf/docs/netcdf-c/nc_005fput_005fvarm_005f-type.html#nc_005fput_005fvarm_005f-type

But in doxygen document, it says "nc_put_varm() function will only write a 
variable of
an atomic type; it will not write user defined types."
http://www.unidata.ucar.edu/software/netcdf/docs/group__variables.html#ga48533a5a1ab3c2e883e6c862720b94ab


I may not fully understand the description for argument imapp in the C 
interface guide.
When I use nc_put_varm(), do I set the values in imapp[] to the distances in 
number of elements
or bytes? I tested a program (extracted below) that uses both nc_put_varm_int() 
and nc_put_varm().
At first, I defined a 1-D integer array variable of size 2 in netCDF file.
The results are different between using nc_put_varm_int() and nc_put_varm().
It looks like in nc_put_varm(), imap[] is in the units of bytes and in 
nc_put_varm_int(), imap[]
is in number of integers.

   int       buf[5]    = {0,1,2,3,4};
   size_t    start[1]  = {0};
   size_t    count[1]  = {2};
   ptrdiff_t stride[1] = {1};
   ptrdiff_t imap[1]   = {4};

   nc_put_varm_int(ncid, varid, start, count, stride, imap, buf);
or
   nc_put_varm    (ncid, varid, start, count, stride, imap, buf);


Command ncdump shows the contents of variable are:
for nc_put_varm_int()
 VAR = 0, 4 ;
for nc_put_varm_()
 VAR = 0, 1 ;

Please clarify if this is correct behavior.

In the C interface guide, nc_put_varm requires "the type of the data in memory 
must match the type of the variable". It sounds to me imap should be the 
distances in units of element numbers, e.g. number of integers in the above 
example.


Thanks.

Wei-keng Liao

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  • Re: [netcdfgroup] nc_put_varm
    • From: Russ Rew