OpenBLAS  0.3.6
About: OpenBLAS is an optimized BLAS (Basic Linear Algebra Subprograms) library based on GotoBLAS2 1.13 BSD version.
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OpenBLAS is an optimized BLAS library based on GotoBLAS2 1.13 BSD version.

Please read the documentation on the OpenBLAS wiki pages:

We provide official binary packages for the following platform:

  • Windows x86/x86_64

You can download them from file hosting on

Download from project homepage,, or check out the code using Git from

Building OpenBLAS requires the following to be installed:

  • GNU Make
  • A C compiler, e.g. GCC or Clang
  • A Fortran compiler (optional, for LAPACK)
  • IBM MASS (optional, see below)

Simply invoking make (or gmake on BSD) will detect the CPU automatically. To set a specific target CPU, use make TARGET=xxx, e.g. make TARGET=NEHALEM. The full target list is in the file TargetList.txt.

Set CC and FC to point to the cross toolchains, and set HOSTCC to your host C compiler. The target must be specified explicitly when cross compiling.


  • On an x86 box, compile this library for a loongson3a CPU:
    make BINARY=64 CC=mips64el-unknown-linux-gnu-gcc FC=mips64el-unknown-linux-gnu-gfortran HOSTCC=gcc TARGET=LOONGSON3A
  • On an x86 box, compile this library for a loongson3a CPU with loongcc (based on Open64) compiler:
    make CC=loongcc FC=loongf95 HOSTCC=gcc TARGET=LOONGSON3A CROSS=1 CROSS_SUFFIX=mips64el-st-linux-gnu- NO_LAPACKE=1 NO_SHARED=1 BINARY=32

A debug version can be built using make DEBUG=1.

The IBM MASS library consists of a set of mathematical functions for C, C++, and Fortran applications that are are tuned for optimum performance on POWER architectures. OpenBLAS with MASS requires a 64-bit, little-endian OS on POWER. The library can be installed as shown:

  • On Ubuntu:
    wget -q -O- | sudo apt-key add -
    echo "deb trusty main" | sudo tee /etc/apt/sources.list.d/ibm-xl-compiler-eval.list
    sudo apt-get update
    sudo apt-get install libxlmass-devel.8.1.5
  • On RHEL/CentOS:
    sudo rpm --import repomd.xml.key
    sudo cp ibm-xl-compiler-eval.repo /etc/yum.repos.d/
    sudo yum install libxlmass-devel.8.1.5

After installing the MASS library, compile OpenBLAS with USE_MASS=1. For example, to compile on Power8 with MASS support: make USE_MASS=1 TARGET=POWER8.

Use PREFIX= when invoking make, for example

make install PREFIX=your_installation_directory

The default installation directory is /opt/OpenBLAS.

Please read GotoBLAS_01Readme.txt.

  • Intel Xeon 56xx (Westmere): Used GotoBLAS2 Nehalem codes.
  • Intel Sandy Bridge: Optimized Level-3 and Level-2 BLAS with AVX on x86-64.
  • Intel Haswell: Optimized Level-3 and Level-2 BLAS with AVX2 and FMA on x86-64.
  • Intel Skylake: Optimized Level-3 and Level-2 BLAS with AVX512 and FMA on x86-64.
  • AMD Bobcat: Used GotoBLAS2 Barcelona codes.
  • AMD Bulldozer: x86-64 ?GEMM FMA4 kernels. (Thanks to Werner Saar)
  • AMD PILEDRIVER: Uses Bulldozer codes with some optimizations.
  • AMD STEAMROLLER: Uses Bulldozer codes with some optimizations.
  • ICT Loongson 3A: Optimized Level-3 BLAS and the part of Level-1,2.
  • ICT Loongson 3B: Experimental
  • ARMv6: Optimized BLAS for vfpv2 and vfpv3-d16 (e.g. BCM2835, Cortex M0+)
  • ARMv7: Optimized BLAS for vfpv3-d32 (e.g. Cortex A8, A9 and A15)
  • ARMv8: Experimental
  • ARM Cortex-A57: Experimental
  • POWER8: Optmized Level-3 BLAS and some Level-1, only with USE_OPENMP=1
  • Z13: Optimized Level-3 BLAS and Level-1,2 (double precision)

Statically link with libopenblas.a or dynamically link with -lopenblas if OpenBLAS was compiled as a shared library.

Environment variables are used to specify a maximum number of threads. For example,



If you compile this library with USE_OPENMP=1, you should set the OMP_NUM_THREADS environment variable; OpenBLAS ignores OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS when compiled with USE_OPENMP=1.

We provide the following functions to control the number of threads at runtime:

void goto_set_num_threads(int num_threads);
void openblas_set_num_threads(int num_threads);

If you compile this library with USE_OPENMP=1, you should use the above functions too.

Please submit an issue in

Please see Changelog.txt to view the differences between OpenBLAS and GotoBLAS2 1.13 BSD version.

  • Please read the FAQ first.
  • Please use GCC version 4.6 and above to compile Sandy Bridge AVX kernels on Linux/MinGW/BSD.
  • Please use Clang version 3.1 and above to compile the library on Sandy Bridge microarchitecture. Clang 3.0 will generate the wrong AVX binary code.
  • Please use GCC version 6 or LLVM version 6 and above to compile Skylake AVX512 kernels.
  • The number of CPUs/cores should less than or equal to 256. On Linux x86_64 (amd64), there is experimental support for up to 1024 CPUs/cores and 128 numa nodes if you build the library with BIGNUMA=1.
  • OpenBLAS does not set processor affinity by default. On Linux, you can enable processor affinity by commenting out the line NO_AFFINITY=1 in Makefile.rule. However, note that this may cause a conflict with R parallel.
  • On Loongson 3A, make test may fail with a pthread_create error (EAGAIN). However, it will be okay when you run the same test case on the shell.
  1. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug.
  2. Fork the OpenBLAS repository to start making your changes.
  3. Write a test which shows that the bug was fixed or that the feature works as expected.
  4. Send a pull request. Make sure to add yourself to

Please read this wiki page.

void openblas_set_num_threads(int num_threads)
Definition: blas_server_win32.c:528
void goto_set_num_threads(int num_threads)
Definition: blas_server_win32.c:484