Hi Wei-keng,
> 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
The older C interface guide describes the intended behavior, but the
doxygen document is currently correct, as there is an explicit test in
libdispatch/dvar{get,put}.c to disallow user-defined types for _varm
functions:
if(vartype > NC_MAX_ATOMIC_TYPE)
return NC_EMAPTYPE;
Since the library seems to work OK for similar _vars functions for
user-defined types, I think the intended behavior for _varm functions
can be restored without too much effort (but the fix won't be in the
upcoming 4.3.2 release). I've created an issue to track the fix:
https://bugtracking.unidata.ucar.edu/browse/NCF-300
> 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.
I think you're right, the imap[] argument for nc_put_varm() should be in
terms of number of elements, not number of bytes. Fixing that bug has
been included in the issue above.
Thanks for reporting the problems!
--Russ
