[hdf-forum] setting chunk dimensions

[Francesc Alted]

Hi Natalie,

A Tuesday 21 October 2008, Natalie Happenhofer escrigué:
> Hi!
> I´m trying to write my data via hyperslabs, ad there is also a nice
> example how to do it on the HDF5.org webpage. I just don´t understand
> how to set the chunk_dims, or, more precisely, what do this chunking
> dimensions do? Here is the part of the example code using the
> chunk-dims:
[clip]
>hsize_t      chunk_dims[2] ={2, 5};
[clip]
> chunk_dims is set to {2,5}, which I don´t understand, because the
> initial dataset is 3x3 and is then extended to 10x3 - why the {2,5}?

Because you told HDF5 that your chunk dimensions are {2,5} (see above).
Chunk sizes don't have nothing to do with the dimensions of your 
dataset, but rather on the way the I/O is done.

I'd recommend you to carefully read the "Datasets" section of the User's 
Guide at:

http://www.hdfgroup.org/HDF5/doc/UG/UG_frame10Datasets.html

and particularly the section labeled as "Chunked".

-- 
Francesc Alted
Freelance Developer & Consultant

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