As far as I know there is no such API available in NetCDF yet.
There is one in PnetCDF called varn APIs that might do what you are asking.
See the API description and examples in the URL below.
http://cucis.ece.northwestern.edu/projects/PnetCDF/doc/pnetcdf-c/ncmpi_005fput_005fvarn_005f_003ctype_003e.html
Please note the APIs are different between PnetCDF and NetCDF.
Wei-keng
On Mar 16, 2017, at 4:44 PM, Ketan Kulkarni wrote:
> Hello!
> I have implemented netcdf4 parllel writing of 4 dimensional(time, z, y, x)
> variable in our application which replaces posix based shared I/O into a
> binary file.
> The data is correctly written into the file.
> As a next step to take the application towards petaflop scale, I am planning
> to implement compute-node level I/O where only one core on each compute node
> will take part in writing the output. I know the start indices and counts
> from each core from the application.
> I have gathered this information on one core of each compute node and I can
> write the gathered data one after the other in a for loop.
> My question is, it possible to write this whole gathered array from the I/O
> core in one single call?
> So far from the documentation I can understand that for nc_put_vara_type
> functions
> the length of start and length of count has to match the dimensions of the
> variable.
> Is it possible to replace this with a start vector and count vector which has
> multiple values corresponding to each block and supply the complete gathered
> array to one single nc_put_vara_type call.
>
> As a side note MPI standard guarantees that the MPI_gather will order the
> data according to ranks. So If I gather the start and count from each core in
> a single vector, they will correspond to each other.
> Thank you and regards,
> Ketan Kulkarni
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