zfp consists of four distinct parts: a compression library written in C, a set of C++ header files that implement compressed arrays and corresponding C wrappers, optional Python and Fortran bindings, and a set of C and C++ examples and utilities. The main compression codec is written in C and should conform to both the ISO C89 and C99 standards. The C++ array classes are implemented entirely in header files and can be included as is, but since they call the compression library, applications must link with libzfp.

zfp is preferably built using CMake, although the core library can also be built using GNU make on Linux, macOS, and MinGW.

zfp conforms to various language standards, including C89, C99, C++98, C++11, and C++14.


zfp requires compiler support for 64-bit integers.

CMake Builds

To build zfp using CMake on Linux or macOS, start a Unix shell and type:

cd zfp-1.0.1
mkdir build
cd build
cmake ..

To also build the examples, replace the cmake line with:


By default, CMake builds will attempt to locate and use OpenMP. To disable OpenMP, type:


To build zfp using Visual Studio on Windows, start a DOS shell and type:

cd zfp-1.0.1
mkdir build
cd build
cmake ..
cmake --build . --config Release

This builds zfp in release mode. Replace ‘Release’ with ‘Debug’ to build zfp in debug mode. See the instructions for Linux on how to change the cmake line to also build the example programs.

GNU Builds

To build zfp using gcc without OpenMP, type:

cd zfp-1.0.1

This builds libzfp as a static library as well as the zfp command-line utility. To enable OpenMP parallel compression, type:



GNU builds expose only limited functionality of zfp. For instance, CUDA and Python support are not included. For full functionality, build zfp using CMake.


To test that zfp is working properly, type:


or using GNU make:

gmake test

If the GNU build or regression tests fail, it is possible that some of the macros in the file Config have to be adjusted. Also, the tests may fail due to minute differences in the computed floating-point fields being compressed, which will be indicated by checksum errors. If most tests succeed and the failures result in byte sizes and error values reasonably close to the expected values, then it is likely that the compressor is working correctly.

Build Targets

To specify which components to build, set the macros below to ON (CMake) or 1 (GNU make), e.g.,


or using GNU make


Regardless of the settings below, libzfp will always be built.


Build all subdirectories; enable all options (except BUILD_SHARED_LIBS). Default: off.


Build libcfp for C bindings to the compressed-array classes. Default: off.


Build zfPy for Python bindings to the C API.

CMake will attempt to automatically detect the Python installation to use. If CMake finds multiple Python installations, it will use the newest one. To specify a specific Python installation to use, set PYTHON_LIBRARY and PYTHON_INCLUDE_DIR on the cmake line:

cmake -DBUILD_ZFPY=ON -DPYTHON_LIBRARY=/path/to/lib/ -DPYTHON_INCLUDE_DIR=/path/to/include/python2.7 ..

CMake default: off. GNU make default: off and ignored.


Build libzFORp for Fortran bindings to the C API. Requires Fortran standard 2018 or later. GNU make users may specify the Fortran compiler to use via

gmake BUILD_ZFORP=1 FC=/path/to/fortran-compiler

Default: off.


Build zfp command-line utility for compressing binary files. Default: on.


Build code examples. Default: off.


Build testzfp tests. Default: on.


Build all unit tests. Default: off.


Build shared objects (.so, .dylib, or .dll files). CMake default: on. GNU make default: off.


On macOS, add OS=mac when building shared libraries with GNU make.


The behavior of zfp can be configured at compile time via a set of macros in the same manner that build targets are specified, e.g.,


64-bit signed and unsigned integer types and their literal suffixes. Platforms on which long int is 32 bits wide may require long long int as type and ll as suffix. These macros are relevant only when compiling in C89 mode. When compiling in C99 mode, integer types are taken from stdint.h. Defaults: long int, l, unsigned long int, and ul, respectively.


CMake and GNU make macro for enabling or disabling OpenMP support. CMake builds will by default enable OpenMP when available. Set this macro to 0 or OFF to disable OpenMP support. For GNU builds, OpenMP is disabled by default. Set this macro to 1 or ON to enable OpenMP support. See also OMPFLAGS in Config in case the compiler does not recognize -fopenmp. For example, Apple clang requires OMPFLAGS=-Xclang -fopenmp, LDFLAGS=-lomp, and an installation of libomp. CMake default: on. GNU make default: off.


CMake macro for enabling or disabling CUDA support for GPU compression and decompression. When enabled, CUDA and a compatible host compiler must be installed. For a full list of compatible compilers, please consult the NVIDIA documentation. If a CUDA installation is in the user’s path, it will be automatically found by CMake. Alternatively, the CUDA binary directory can be specified using the CUDA_BIN_DIR environment variable. CMake default: off. GNU make default: off and ignored.


Experimental feature. By default, zfp coefficients are truncated, not rounded, which can result in biased errors (see FAQ #30). To counter this, two rounding modes are available: ZFP_ROUND_FIRST (round during compression; analogous to mid-tread quantization) and ZFP_ROUND_LAST (round during decompression; analogous to mid-riser quantization). With ZFP_ROUND_LAST, the values returned on decompression are slightly modified (and usually closer to the original values) without impacting the compressed data itself. This rounding mode works with all compression modes. With ZFP_ROUND_FIRST, the values are modified before compression, thus impacting the compressed stream. This rounding mode tends to be more effective at reducing bias, but is invoked only with fixed-precision and fixed-accuracy compression modes. Both of these rounding modes break the regression tests since they alter the compressed or decompressed representation, but they may be used with libraries built with the default rounding mode, ZFP_ROUND_NEVER, and versions of zfp that do not support a rounding mode with no adverse effects. Note: ZFP_ROUNDING_MODE is currently supported only by the serial and omp execution policies. Default: ZFP_ROUND_NEVER.


Experimental feature. When enabled, this feature takes advantage of the error reduction associated with proper rounding; see ZFP_ROUNDING_MODE. The reduced error due to rounding allows the tolerance in fixed-accuracy mode to be satisfied using fewer bits of compressed data. As a result, when enabled, the observed maximum absolute error is closer to the tolerance and the compression ratio is increased. This feature requires the rounding mode to be ZFP_ROUND_FIRST or ZFP_ROUND_LAST and is supported only by the serial and omp execution policies. Default: undefined/off.


When enabled, blocks consisting solely of subnormal floating-point numbers (tiny numbers close to zero) are treated as blocks of all zeros (DAZ = denormals-are-zero). The main purpose of this option is to avoid the potential for floating-point overflow in the zfp implementation that may occur in step 2 of the lossy compression algorithm when converting to zfp’s block-floating-point representation (see Issue #119). Such overflow tends to be benign but loses all precision and usually results in “random” subnormals upon decompression. When enabled, compressed streams may differ slightly but are decompressed correctly by libraries built without this option. This option may break some regression tests. Note: ZFP_WITH_DAZ is currently ignored by all execution policies other than serial and omp. Default: undefined/off.


Use aligned memory allocation in an attempt to align compressed blocks on hardware cache lines. Default: undefined/off.


Use a two-way skew-associative rather than direct-mapped cache. This incurs some overhead that may be offset by better cache utilization. Default: undefined/off.


Use a simpler hash function for cache line lookup. This is faster but may lead to more collisions. Default: undefined/off.


Enable cache profiling to gather and print statistics on cache hit and miss rates. Default: undefined/off.


Unsigned integer type used for buffering bits. Wider types tend to give higher performance at the expense of lower bit rate granularity. For portability of compressed files between little and big endian platforms, BIT_STREAM_WORD_TYPE should be set to uint8. Default: uint64.


CMake macro for indirectly setting BIT_STREAM_WORD_TYPE. Valid values are 8, 16, 32, 64. Default: 64.


Enable support for strided bit streams that allow for non-contiguous memory layouts, e.g., to enable progressive access. Default: undefined/off.


Macro for renaming the outermost cfp namespace, e.g., to avoid name clashes. Default: cfp.


Path to the Python library, e.g., /usr/lib/ CMake default: undefined/off. GNU make default: off and ignored.


Path to the Python include directory, e.g., /usr/include/python2.7. CMake default: undefined/off. GNU make default: off and ignored.


The core zfp library and compressed arrays require only a C89 and C++98 compiler. The optional components have additional dependencies, as outlined in the sections below.


CMake builds require version 3.9 or later. CMake is available here.


OpenMP support requires OpenMP 2.0 or later.


CUDA support requires CUDA 7.0 or later, CMake, and a compatible host compiler (see ZFP_WITH_CUDA).


The zfp C library and cfp C wrappers around the compressed-array classes conform to the C90 standard (ISO/IEC 9899:1990). The C++ classes conform to the C++98 standard (ISO/IEC 14882:1998).


The optional Python bindings require CMake and the following minimum versions:

  • Python: Python 2.7 & Python 3.5

  • Cython: 0.22

  • NumPy: 1.8.0

The necessary dependencies can be installed using pip and the zfp requirements.txt:

pip install -r $ZFP_ROOT/python/requirements.txt


The optional Fortran bindings require a Fortran 2018 compiler.