LAPACK++ Installation Notes
================================================================================

[TOC]

Synopsis
--------------------------------------------------------------------------------

Configure and compile the LAPACK++ library and its tester,
then install the headers and library.

Option 1: Makefile

    make && make install

Option 2: CMake

    # LAPACK++ requires BLAS++, from
    # https://github.com/icl-utk-edu/blaspp
    cd /path/to/blaspp
    mkdir build && cd build
    cmake ..
    make && make install

    # After installing BLAS++ above
    cd /path/to/lapackpp
    mkdir build && cd build
    cmake ..
    make && make install

Environment variables (Makefile and CMake)
--------------------------------------------------------------------------------

Standard environment variables affect both Makefile (configure.py) and CMake.
These include:

    LD                  Linker; defaults to CXX
    CXX                 C++ compiler
    CXXFLAGS            C++ compiler flags
    LDFLAGS             linker flags
    CPATH               compiler include search path
    LIBRARY_PATH        compile-time library search path
    LD_LIBRARY_PATH     runtime library search path
    DYLD_LIBRARY_PATH   runtime library search path on macOS
    CUDA_PATH           path to CUDA, e.g., /usr/local/cuda
    CUDA_HOME           also recognized for path to CUDA
    ROCM_PATH           path to ROCm, e.g., /opt/rocm


Options (Makefile and CMake)
--------------------------------------------------------------------------------

See the BLAS++ INSTALL.md for BLAS++ specific options. Since the LAPACK library
is often bundled with the BLAS library, such as -lopenblas, it should be specified in BLAS++.

LAPACK++ specific options include (all values are case insensitive):

    lapack
        LAPACK libraries to search for.
        LAPACK is often included in the BLAS library (e.g., -lopenblas contains both),
        so there is usually no need to specify this. One or more of:
        auto            search for all libraries (default)
        generic         generic -llapack

    LAPACK_LIBRARIES
        Specify the exact LAPACK libraries, overriding the built-in search.
        Again, there is usually no need to specify this. E.g.,
        cmake -DLAPACK_LIBRARIES='-lopenblas' ..

    gpu_backend
        BLAS++ must be built with the same GPU backend.
        auto            (default) auto-detect CUDA, HIP/ROCm, or SYCL
        cuda            build with CUDA support
        hip             build with HIP/ROCm support
        sycl            build with SYCL and oneMKL support
        none            do not build with GPU backend

    color
        Whether to use ANSI colors in output. One of:
        auto            uses color if output is a TTY
                        (default with Makefile; not support with CMake)
        yes             (default with CMake)
        no

With Makefile, options are specified as environment variables or on the
command line using `option=value` syntax, such as:

    python3 configure.py lapack=generic

With CMake, options are specified on the command line using
`-Doption=value` syntax (not as environment variables), such as:

    cmake -Dblas=mkl ..


Makefile Installation
--------------------------------------------------------------------------------

Available targets:

    make           - configures (if make.inc is missing),
                     then compiles the library and tester
    make config    - configures LAPACK++, creating a make.inc file
    make lib       - compiles the library (lib/liblapackpp.so)
    make tester    - compiles test/tester
    make check     - run basic checks using tester
    make docs      - generates documentation in docs/html/index.html
    make install   - installs the library and headers to ${prefix}
    make uninstall - remove installed library and headers from ${prefix}
    make clean     - deletes object (*.o) and library (*.a, *.so) files
    make distclean - also deletes make.inc and dependency files (*.d)


### Options

    make config [options]
    or
    python3 configure.py [options]

Runs the `configure.py` script to detect your compiler and library properties,
then creates a make.inc configuration file. You can also manually edit the
make.inc file. Options are name=value pairs to set variables.

Besides the Environment variables and Options listed above, additional
options include:

    static
        Whether to build as a static or shared library.
        0               shared library (default)
        1               static library

    prefix
        Where to install, default /opt/slate.
        Headers go   in ${prefix}/include,
        library goes in ${prefix}/lib${LIB_SUFFIX}

These can be set in your environment or on the command line, e.g.,

    python3 configure.py CXX=g++ prefix=/usr/local

Configure assumes environment variables are set so your compiler can find BLAS
and LAPACK libraries. For example:

    export LD_LIBRARY_PATH="/opt/my-blas/lib64"  # or DYLD_LIBRARY_PATH on macOS
    export LIBRARY_PATH="/opt/my-blas/lib64"
    export CPATH="/opt/my-blas/include"
    or
    export LDFLAGS="-L/opt/my-blas/lib64 -Wl,-rpath,/opt/my-blas/lib64"
    export CXXFLAGS="-I/opt/my-blas/include"

On some systems, loading the appropriate module will set these flags:

    module load my-blas


### Vendor notes

Intel MKL provides scripts to set these flags, e.g.:

    source /opt/intel/bin/compilervars.sh intel64
    or
    source /opt/intel/mkl/bin/mklvars.sh intel64

IBM ESSL provides only a subset of LAPACK functions,
so Netlib LAPACK is also required.


### Manual configuration

If you have a specific configuration that you want, set CXX, CXXFLAGS, LDFLAGS,
and LIBS, e.g.:

    export CXX="g++"
    export CXXFLAGS="-I${MKLROOT}/include -fopenmp"
    export LDFLAGS="-L${MKLROOT}/lib/intel64 -Wl,-rpath,${MKLROOT}/lib/intel64 -fopenmp"
    export LIBS="-lmkl_gf_lp64 -lmkl_gnu_thread -lmkl_core -lm"

These can also be set when running configure:

    make config CXX=g++ \
                CXXFLAGS="-I${MKLROOT}/include -fopenmp" \
                LDFLAGS="-L${MKLROOT}/lib/intel64 -Wl,-rpath,${MKLROOT}/lib/intel64 -fopenmp" \
                LIBS="-lmkl_gf_lp64 -lmkl_gnu_thread -lmkl_core -lm"

Note that all test programs are compiled with those options, so errors may cause
configure to fail.

If you experience unexpected problems, please see config/log.txt to diagnose the
issue. The log shows the option being tested, the exact command run, the
command's standard output (stdout), error output (stderr), and exit status. All
test files are in the config directory.


CMake Installation
--------------------------------------------------------------------------------

LAPACK++ requires BLAS++ and inherits its dependencies from BLAS++, so BLAS++ must be
installed first via CMake, before running CMake for LAPACK++. Information and
installation instructions can be found at https://github.com/icl-utk-edu/blaspp.
Briefly:

    # LAPACK++ requires BLAS++, from
    # https://github.com/icl-utk-edu/blaspp
    cd /path/to/blaspp
    cmake [-DCMAKE_INSTALL_PREFIX=/path/to/install] [options] ..
    make
    make install

The CMake script enforces an out-of-source build. Create a build
directory under the LAPACK++ root directory:

    # After installing BLAS++ above
    cd /path/to/lapackpp
    mkdir build && cd build
    cmake [-DCMAKE_INSTALL_PREFIX=/path/to/install] [options] ..
    make
    make install

LAPACK++ should find BLAS++ if it is installed in a system default
location (e.g., /usr/local), or their install prefix is the same. If
LAPACK++ can't find BLAS++, you can point to its directory:

    cmake -DCMAKE_PREFIX_PATH=/path/to/install [options] ..
    or
    cmake -Dblaspp_DIR=/path/to/install/lib/blaspp [options] ..

LAPACK++ uses the TestSweeper library (https://github.com/icl-utk-edu/testsweeper)
to run its tests. If CMake doesn't find TestSweeper, it will be
downloaded and compiled. To use a different TestSweeper build that was
not installed, you can point to its directory.

    cmake -Dtestsweeper_DIR=/path/to/testsweeper/build [options] ..


### Options

Besides the Environment variables and Options listed above, additional
options include:

    build_tests
        Whether to build test suite (test/tester).
        Requires TestSweeper, CBLAS, and LAPACKE. One of:
        yes (default)
        no

    use_cmake_find_lapack
        Whether to use CMake's FindLAPACK, instead of LAPACK++ search.
        Again, as LAPACK is often included in the BLAS library,
        there is usually no need to specify this. One of:
        yes
        no (default)
        If BLA_VENDOR is set, it automatically uses CMake's FindLAPACK.

    BLA_VENDOR
        Use CMake's FindLAPACK, instead of LAPACK++ search. For values, see:
        https://cmake.org/cmake/help/latest/module/FindLAPACK.html

Standard CMake options include:

    BUILD_SHARED_LIBS
        Whether to build as a static or shared library. One of:
        yes             shared library (default)
        no              static library

    CMAKE_INSTALL_PREFIX (alias prefix)
        Where to install, default /opt/slate.
        Headers go   in ${prefix}/include,
        library goes in ${prefix}/lib

    CMAKE_PREFIX_PATH
        Where to look for CMake packages such as BLAS++ and TestSweeper.

    CMAKE_BUILD_TYPE
        Type of build. One of:
        [empty]         default compiler optimization          (no flags)
        Debug           no optimization, with asserts          (-O0 -g)
        Release         optimized, no asserts, no debug info   (-O3 -DNDEBUG)
        RelWithDebInfo  optimized, no asserts, with debug info (-O2 -DNDEBUG -g)
        MinSizeRel      Release, but optimized for size        (-Os -DNDEBUG)

    CMAKE_MESSAGE_LOG_LEVEL (alias log)
        Level of messages to report. In ascending order:
        FATAL_ERROR, SEND_ERROR, WARNING, AUTHOR_WARNING, DEPRECATION,
        NOTICE, STATUS, VERBOSE, DEBUG, TRACE.
        Particularly, DEBUG or TRACE gives useful information.

With CMake, options are specified on the command line using
`-Doption=value` syntax (not as environment variables), such as:

    # in build directory
    cmake -Dbuild_tests=no -DCMAKE_INSTALL_PREFIX=/usr/local ..

Alternatively, use the `ccmake` text-based interface or the CMake app GUI.

    # in build directory
    ccmake ..
    # Type 'c' to configure, then 'g' to generate Makefile

To re-configure CMake, you may need to delete CMake's cache:

    # in build directory
    rm CMakeCache.txt
    # or
    rm -rf *
    cmake [options] ..

To debug the build, set `VERBOSE`:

    # in build directory, after running cmake
    make VERBOSE=1