Compiling Qbics
====================

To compile Qbics, please follow the instructions step-by-step.

One-key Build
-------------------




Fundamental Components
-------------------------

The following fundamental components are needed:

- ``gcc``, version >= 8.0;
- ``make``, version >= 3.8;
- ``OpenMPI``, version >= 3.0, if OpenMPI is enabled;
- ``nvcc``, version >= 11.0, if CUDA is enabled;

Third-party Libraries
----------------------

``Boost`` and ``Eigen``
++++++++++++++++++++++++++++

``Boost`` and ``Eigen`` are two header-only libraries that do not need compilation. They can be obtained from:

- ``Boost``: https://www.boost.org/ 
- ``Eigen``: https://eigen.tuxfamily.org/

After you download the source files, decompress them. You will find directories called ``boost`` and ``Eigen``, respectively. Copy ``boost`` and ``Eigen`` to a suitable path, say ``/home/zhang/libs``. This will be the value for ``$INCBOOST`` and ``$INCEIGEN`` in the corresponding Makefile.

Of course, if your system has already installed ``Boost`` and ``Eigen`` somewhere, just use those then.

``libxc``
+++++++++++++

``libxc`` is a density functional library. It can be obtained from https://libxc.gitlab.io/. You can compile it using the following instructions:

.. code-block:: bash

    $ bzip2 -d libxc-x.x.x.tar.bz2
    $ tar -xvf libxc-x.x.x.tar
    $ cd libxc-x.x.x
    $ autoreconf -i
    $ ./configure --prefix=/home/zhang/libs/libxc
    $ make -CFLAGS="-std=c99 -O2"
    $ make install

Now, all ``libxc`` files are available in ``/home/zhang/libs/libxc``.

Of course, if your system has already installed ``libxc`` somewhere, just use it then.

``libfftw3``
+++++++++++++

``libfftw3`` is an efficient library for fast Fourier transformation. It can be obtained from https://www.fftw.org/download.html. You can compile it using the following instructions:

.. code-block:: bash

    $ tar -xzf fftw-x.x.x.tar.gz
    $ cd fftw-x.x.x
    $ ./configure --prefix=/home/zhang/libs/fftw --enable-openmp
    $ make
    $ make install

Now, all ``libfftw3`` files are available in ``/home/zhang/libs/fftw``.

Of course, if your system has already installed ``libfftw3`` somewhere, just use it then.

``plumed``
+++++++++++++++

``plumed`` is a library for enhanced sampling algorithms. It can be obtained from https://github.com/plumed/plumed2/releases/. You can compile it using the following instructions:

.. code-block:: bash

    $ unzip plumed2-x.x.x.zip
    $ cd plumed2-x.x.x
    $ ./configure --prefix=/home/zhang/libs/plumed2 --disable-mpi --disable-external-lapack --disable-external-blas
    $ make
    $ make install

Of course, if your system has already installed ``plumed`` somewhere, just use it then.

``dftd3-lib``
+++++++++++++++

``dftd3-lib`` is a library for carrying out DFT-D3 calculations. It can be obtained from https://github.com/dftbplus/dftd3-lib. You can compile it using the following instructions:

.. code-block:: bash

    $ unzip dftd3-lib-master.zip
    $ cd dftd3-lib-master
    $ make lib
    $ cp lib /home/zhang/libs/dftd3-lib -r

Of course, if your system has already installed ``dftd3-lib`` somewhere, just use it then.


Edit Makefile
------------------------------

After decompressing the source file archive, you can find several Makefiles:

+------------------------+-----------------------------------------------------------+
|``Makefile-win-cpu``    | Native Windows version, OpenMP parallelized.              |
+------------------------+-----------------------------------------------------------+
|``Makefile-linux-cpu``  | Linux version, OpenMP parallelized.                       |
+------------------------+-----------------------------------------------------------+
|``Makefile-linux-gpu``  | Linux version, OpenMP parallelized, GPU enabled.          |
+------------------------+-----------------------------------------------------------+

Open the suitable one, say ``Makefile-linux-cpu``, you can find the following:

.. code-block:: bash
    :linenos:
    :caption: Makefile-linux-cpu

    CODEINFO = -DCodeCommit="\"`git rev-parse HEAD`\"" \
    -DCodeFlag="\"official version\"" \
    -DCodeMajorVer=0 \
    -DCodeMinorVer=1 \
    -DCodeUser="\"`whoami | sed 's/\\\\/\\\\\\\\/g'`\"" \
    -DCodeMachine="\"`hostname`\"" \
    -DCodeCompiler="\"`$(CXX) --version | head -n 1`"\" \
    -DCodeCompFlags="\"$(CXXFLAG)"\" \
    -DCodeLibs="\"$(LIBS)"\" \
    -DOSLinux \
    -DNDEBUG

    CXX     = g++
    CXXFLAG = -O2 -fno-exceptions --std=c++17 -fopenmp -ffast-math -fno-finite-math-only -fexpensive-optimizations -Wall -mavx2 -mfma
    CC      = gcc
    CCFLAG  = -O2 -fopenmp -Wall
    FC      = gfortran
    FCFLAG  = -O2 -fopenmp -Wall
    NCC     = nvcc
    NCCFLAG = -O2 -use_fast_math -arch=compute_75 -code=sm_75
    
    # Third-party library
    LIBGNU    = -lgfortran -lquadmath -static -Wl,--whole-archive -lpthread -Wl,--no-whole-archive
    LIBXC     = /opt/libxc-5.2.3/lib/libxc.a
    LIBFFTW3  = /opt/fftw-3.3.10/lib/libfftw3.a /opt/fftw-3.3.10/lib/libfftw3_omp.a
    LIBDFTD   = /opt/dftd3-3.2/dftd3-lib-0.9/lib/libdftd3.a
    LIBJSON   = /opt/jsoncpp/lib/libjsoncpp.a
    LIBLEPTON = /opt/lepton/liblepton.a
    LIBCUDA   =
    LIBSPONGE = 
    LIBS      = $(LIBXC) $(LIBFFTW3) $(LIBDFTD) $(LIBJSON) $(LIBLEPTON) $(LIBGNU)
    
    # Third-party include
    INCBOOST  = -I/opt/include/boost_1_78_0
    INCEIGEN  = -I/opt/include/eigen-3.4.0
    INCLIBXC  = -I/opt/libxc-5.2.3/include
    INCFFTW3  = -I/opt/fftw-3.3.10/include
    INCDFTD   = -I/opt/dftd3-3.2/dftd3-lib-0.9/lib
    INCJSON   = -I/opt/jsoncpp/include
    INCLEPTON = -I/opt/lepton
    INCCUDA   = -I/usr/local/cuda-11.4/targets/x86_64-linux/include
    INCS      = $(INCBOOST) $(INCEIGEN) $(INCLIBXC) $(INCFFTW3) $(INCDFTD) $(INCJSON) $(INCLEPTON)


- You can modify the macro ``CodeFlag`` to give the code a unique identifier.
- You can change ``CXXFLAG``, ``FCFLAG`` or ``NCCFLAG`` to add suitable optimization options according to your systems. 
- You should change ``LIBXC``, ``INCBOOST``, etc. to provide the correct paths of libraries and header files.

Compile
-------------------------

After editing your Makefile, say ``Makefile-linux-cpu``, just run the following command:

.. code-block:: bash

    $ make -f Makefile-linux-cpu -j

After a long time, everything is ready in ``bin``. You can copy ``bin`` to anywhere you like.