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The package provides a source ofBLAS andLAPACK viaOpenBLAS.

The following Cargo features are supported:

• cache to build in a shared directory instead oftarget (see below),
• cblas to build CBLAS (enabled by default),
• lapacke to build LAPACKE (enabled by default),
• static to link to OpenBLAS statically,
• system to skip building the bundled OpenBLAS.

Note: On Windows, OpenBLAS can not be built from source. Thesystem feature issupposed to be used.

If you want to build OpenBLAS from source, you need to have the following dependenciesinstalled:

• HOSTCC compiler (e.g.,gcc,clang, oricc),
• make,
• CC compiler of the target architecture (e.g.,aarch64-linux-gnu-gcc foraarch64),
• Fortran compiler of the target architecture(e.g.,gfortran,flang, orifort),if there is no Fortran compiler detected, the flagNOFORTRAN should be set to1andOpenBLAS will only compile BLAS and f2c-converted LAPACK. For more information,please refer to theUse f2c translations of LAPACK when no Fortran compiler is available.

Thecache feature allows the OpenBLAS build products to be reused betweencrates that have differenttarget directories. This avoids rebuilding OpenBLASunnecessarily. However, this also preventscargo clean from working properly,since the aforementioned build products will not be removed by the command.

The OpenBLAS binary will be placed at${XDG_DATA_HOME}/openblas_build/[hash of build configure object]. For example, build with LAPACK and build withoutLAPACK will be placed on different directories. If you build OpenBLAS as ashared library, you need to add the above directory toLD_LIBRARY_PATH (forLinux) orDYLD_LIBRARY_PATH (for macOS). Since build from source is notsupported on Windows (see next section), this feature is also not supported.

On Windows,openblas-src relies onvcpkg to find OpenBLAS. Before building,you must have the correct OpenBLAS installed for your target triplet and kind oflinking. For instance, to link dynamically for thex86_64-pc-windows-msvctoolchain, installopenblas for thex64-windows triplet:

vcpkg install openblas --triplet x64-windows

To link OpenBLAS statically, installopenblas for thex64-windows-static-md triplet:

vcpkg install openblas --triplet x64-windows-static-md

To link OpenBLAS and C Runtime (CRT) statically, installopenblas for thex64-windows-static triplet:

vcpkg install openblas --triplet x64-windows-static

and build with+crt-static option

RUSTFLAGS='-C target-feature=+crt-static' cargo build --target x86_64-pc-windows-msvc

Please see the"Static and dynamic C runtimes" in The Rust reference for detail.

Theopenblas-src crate will detect and use proxy settings from your environmentvariables, such ashttp_proxy andhttps_proxy to download necessary dependencies.

According to theOpenbLAS build system, the variables used by OpenBLAS could bepassed through environment, such asDYNAMIC_LIST,NUM_THREADS.

HOWEVER, for some of the variables, theopenblas-src crate rename them toothers to avoid conflicts with the existing envs. The following is the list ofthe variables that are renamed:

Apart from providing the--target option tocargo build, one also has tospecify thecross-compilation variables of OpenBLAS.They can be set as environment variables forcargo build using theOPENBLAS_prefix as follows:OPENBLAS_CC,OPENBLAS_FC,OPENBLAS_HOSTCC, andOPENBLAS_TARGET.

If you do not set these variables, theopenblas-build will try to detect them.

ForOPENBLAS_TARGET, the basic target that corresponds to the arch of--targetwill be used.

ForOPENBLAS_CC andOPENBLAS_HOSTCC, thecc crate will be used to detectthe compiler. Please refer to thecc documentationfor more information.

ForOPENBLAS_FC,openblas-build will try to detect the compiler through theOPENBLAS_CC set above. It will replace thegcc withgfortran,clang withflang, andicc withifort and then test if the Fortran compiler exists.

Note: If there is no Fortran compiler detected, the build flagNOFORTRAN willbe set to1 andOpenBLAS will only compile BLAS and f2c-converted LAPACK.For more information, please refer to theUse f2c translations of LAPACK when no Fortran compiler is available.

Your contribution is highly appreciated. Do not hesitate to open an issue or apull request. Note that any contribution submitted for inclusion in the projectwill be licensed according to the terms given inLICENSE.md.