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Today’s HPC applications are producing extremely large amounts of data, thus it is necessary to use an efficient compression before storing them to parallel file systems.

We developed the error-bounded HPC data compressor, by proposing a novel HPC data compression method that works very effectively on compressing large-scale HPC data sets.

The key features of SZ are listed below.

• Compression: Input: a data set (or a floating-point array) with error-bound requirements; Output: the compressed byte stream

  Decompression: input: the compressed byte stream ; Output: the original data set with the compression error of each data point being within a pre-specified error bound ∆.

• SZ supports C and Fortran.

• SZ supports two types of error bounds.

The users can set either absolute error bound or relative error bound, or a combination of the two bounds （with operator AND or OR).

The absolute error bound (denoted δ) is a constant, such as 1E-6. That is, the decompressed data Di′ must be in the range [Di − δ,Di + δ], where Di′ is referred as the decompressed value and Di is the original data value. As for the relative error bound, it is a linear function of the global data value range size, i.e., ∆=λr, where λ(∈(0,1)) and r refer to error bound ratio and range size respectively. For example, given a set of data, the range size r is equal to max (Di )− min (Di ), and the error bound can be written as λ( max (Di )− min (Di )). The relative error bound allows to make sure that the compression error for any data point must be no greater than λ×100 percentage of the global data value range size.

• Detailed usage and examples can be found under the directories doc/user-guide.pdf and example/ respectively, in the package.