# Tests and Examples

The tests directory contains a few simple tests of the H5Z-ZFP filter some of which also serve as decent examples.

The test client, test_write.c is compiled a couple of different ways. One target is `test_write_plugin` which demonstrates the use of this filter as a standalone plugin. The other target, `test_write_lib`, demonstrates the use of the filter as an explicitly linked library. By default, these test a simple 1D array with and without ZFP compression using either the Generic Interface (for plugin) or the Properties Interface (for library). You can use the code there as an example of using the ZFP filter either as a plugin or as a library. However, these also include some advanced usages for 4D and 6D, time-varying (e.g. extendable) datasets. The command `test_write_lib help` or `test_write_plugin help` will print a list of the example’s options and how to use them.

## Write Test Options

    ./test/test_write_lib --help
        ifile=""                                  set input filename
        ofile="test_zfp.h5"                      set output filename

    1D dataset generation arguments...
        npoints=1024             set number of points for 1D dataset
        noise=0.001         set amount of random noise in 1D dataset
        amp=17.7             set amplitude of sinusoid in 1D dataset
        chunk=256                      set chunk size for 1D dataset
        doint=0                              also do integer 1D data

    ZFP compression parameters...
        zfpmode=3        (1=rate,2=prec,3=acc,4=expert,5=reversible)
        rate=4                      set rate for rate mode of filter
        acc=0               set accuracy for accuracy mode of filter
        prec=11       set precision for precision mode of zfp filter
        minbits=0          set minbits for expert mode of zfp filter
        maxbits=4171       set maxbits for expert mode of zfp filter
        maxprec=64         set maxprec for expert mode of zfp filter
        minexp=-1074        set minexp for expert mode of zfp filter

    Advanced cases...
        highd=0                                          run 4D case
        sixd=0          run 6D extendable case (requires ZFP>=0.5.4)
        help=0                                     this help message

The test normally just tests compression of 1D array of integer and double precision data of a sinusoidal array with a small amount of additive random noise. The `highd` test runs a test on a 4D dataset where two of the 4 dimensions are not correlated. This tests the plugin’s ability to properly set chunking for HDF5 such that chunks span only correlated dimensions and have non-unity sizes in 3 or fewer dimensions. The `sixd` test runs a test on a 6D, extendable dataset representing an example of using ZFP for compression along the time axis.

There is a companion, test_read.c which is compiled into `test_read_plugin` and `test_read_lib` which demonstrates use of the filter reading data as a plugin or library. Also, the commands `test_read_lib help` and `test_read_plugin help` will print a list of the command line options.

To use the plugin examples, you need to tell the HDF5 library where to find the H5Z-ZFP plugin with the `HDF5_PLUGIN_PATH` environment variable. The value you pass is the path to the directory containing the plugin shared library.

Finally, there is a Fortran test example, test_rw_fortran.F90. The Fortran test writes and reads a 2D dataset. However, the Fortran test is designed to use the filter only as a library and not as a plugin. The reason for this is that the filter controls involve passing combinations of integer and floating point data from Fortran callers and this can be done only through the Properties Interface, which by its nature requires any Fortran application to have to link with an implementation of that interface. Since we need to link extra code for Fortran, we may as well also link to the filter itself alleviating the need to use the filter as a plugin. Also, if you want to use Fortran support, the HDF5 library must have, of course, been configured and built with Fortran support as well.

In addition, a number tests are performed in the Makefile which test the plugin by using some of the HDF5 tools such as `h5dump` and `h5repack`. Again, to use these tools to read data compressed with the H5Z-ZFP filter, you will need to inform the HDF5 library where to find the filter plugin. For example..

    env HDF5_PLUGIN_PATH=<dir> h5ls test_zfp.h5

Where `<dir>` is the relative or absolute path to a directory containing the filter plugin shared library.