compression does not work well on variable length data. the data is
larger because
of the overhead from storing the compression information.
On 2/5/2013 4:02 PM, heatherk wrote:
Hi,
I'm trying to write several array of Strings with compression using the
lower level H5 functions. However, I'm finding that my files are larger
with compression. Has anyone experienced this? I wasn't sure how to chunk
an array of length 8 so i tried cutting it in half.
I copied and pasted parts of my code below:
String[] array = new String[8];
....
long[] dims = { array.length };
long[] chunk_dims = {array.length/2};
...
// create type id
try {
type_id = H5.H5Tcopy(HDF5Constants.H5T_C_S1);
H5.H5Tset_size(type_id, HDF5Constants.H5T_VARIABLE);
}
catch (Exception e) {
e.printStackTrace();
}
// Create the dataset creation property list, add the gzip
compression
// filter.
try {
dcpl_id = H5.H5Pcreate(HDF5Constants.H5P_DATASET_CREATE);
if (dcpl_id >= 0) {
H5.H5Pset_deflate(dcpl_id, 9);
// Set the chunk size.
H5.H5Pset_chunk(dcpl_id, 1, chunk_dims);
}
}
catch (Exception e) {
e.printStackTrace();
}
try {
if ( (dataspace_id >= 0)) {
dataset_id = H5.H5Dcreate(file_id, NAME,
type_id, dataspace_id,
HDF5Constants.H5P_DEFAULT, dcpl_id,
HDF5Constants.H5P_DEFAULT);
}
}
catch (Exception e) {
e.printStackTrace();
}
--
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