Peter Lindstrom

Poor compression & quality for difficult-to-compress data

12

I am doing some compression studies that involve difficult-to-compress (even incompressible) data. Consider the chaotic data generated by the logistic map _x__i_+1 = 4 _x__i_ (1 - _x__i_): ``` #include...

Incorrect treatment of array dimensions

15

First, a big thanks for making these fpzip wrappers available! Skimming the code and seeing user comments about the need to transpose arrays, I wanted to get to the root...

The main help page says array dimensions should be specified in Fortran order: https://github.com/rballester/tthresh/blob/02df038c6eb9e8003201cb1bd82c678387e4b4ec/src/tthresh.hpp#L98 But when specifying fewer than three dimensions, the documentation says C order: https://github.com/rballester/tthresh/blob/02df038c6eb9e8003201cb1bd82c678387e4b4ec/src/tthresh.cpp#L187-L188

One cannot specify target rms error in scientific notation, e.g., as `-r 1e-6`. Rather, this must be specified as `-r 0.000001`. This becomes cumbersome when integrating tthresh with other tools...

PWE tolerance is violated when very small

9

**Describe the bug** The bug occurs for data with a very small range near single-precision machine epsilon and when the tolerance is smaller than the smallest representable single-precision positive number....

Compression fails for large quantization values

1

Sperr has difficulties compressing certain data sets when the quantization level is high. For instance, using the Nyx temperature field from [SDRBench](https://sdrbench.github.io), the following fails: ``` compressor_3d --dims 512 512...

Document how to use H5Z-ZFP with netCDF-4

2

It would be nice to have documentation on how to use H5Z-ZFP in the context of netCDF-4. I've spent the last couple of days struggling with making this work, and...

The documentation of how H5Z-ZFP encodes `cd_values` suggests that double-precision values are type punned as two unsigned 32-bit integers in the "wrong" order. It says: "A/B are high/low 32-bit words...