.. _install-ferrox:

ELEQTRONeX
=====

.. raw:: html

   <style>
   .rst-content section>img {
       width: 30px;
       margin-bottom: 0;
       margin-top: 0;
       margin-right: 15px;
       margin-left: 15px;
       float: left;
   }
   </style>

Our community is here to help.
Please `report installation problems <https://github.com/AMReX-Microelectronics/ELEQTRONeX/issues/new>`_ in case you are stuck.

Follow these instructions for compilation.

1. Download 
-----------

To download the codes in your local linux system or on a specific high-performance computing (HPC) system:

Download AMReX Repository as

.. code-block:: bash
   
   git clone git@github.com:AMReX-Codes/amrex.git

Download ELEQTRONeX Repository in the folder hierarchy level as AMReX as

.. code-block:: bash

   git@github.com:AMReX-Microelectronics/ELEQTRONeX.git

2. Build Parameters
-------------------

Navigate to the ``Exec/`` folder of ELEQTRONeX and execute 

.. code-block:: bash

   make -j <np>
Replace <np> with the number of processes you want to use. 

To build with MPI and CUDA, ensure that either MPICH or OpenMPI, along with the appropriate CUDA modules, are installed and loaded. In the ``GNUmakefile`` located in the ``Exec/`` directory, set ``USE_MPI=TRUE`` to enable MPI support, ``USE_OMP=FALSE`` to disable OpenMP, and ``USE_CUDA=TRUE`` to activate CUDA support for GPU utilization.

Other flags are explained below, with their default values shown:

- ``AMREX_HOME ?= ../../amrex`` specifies the location of the AMReX library.
- ``DEBUG=FALSE`` sets the debug mode.
- ``USE_HYPRE=FALSE`` can be used to set ``hypre`` for the multigrid bottom solver. Installation instructions for ``hypre`` are provided `here <https://amrex-codes.github.io/amrex/tutorials_html/Hypre_Install.html>`_.
- ``COMP=gnu`` sets the GNU compiler.
- ``DIM=3`` builds the code for 3D domain.
- ``CXXSTD=c++17`` sets  C++17 for compilation.
- ``TINY_PROFILE=FALSE`` is used to enable the AMReX profiler.

Set the following flags based on your configuration needs:

- ``USE_EB=TRUE`` if the input file sets embedded boundaries.
- ``USE_TRANSPORT=TRUE`` for enabling the transport solver, which uses the nonequilibrium Green's function (NEGF) method.
- ``COMPUTE_GREENS_FUNCTION_OFFDIAG_ELEMS=FALSE`` and ``COMPUTE_SPECTRAL_FUNCTION_OFFDIAG_ELEMS=FALSE`` to switch off computations and storage of off-diagonal elements of Green's and spectral functions in the NEGF solver.
- ``BROYDEN_PARALLEL=TRUE`` uses an efficient parallel version of the Broyden's algorithm for self-consistency between electrostatics and NEGF modules.
- ``TIME_DEPENDENT=TRUE`` builds the code for accepting voltages on the embedded boundaries with varying values, for example setting a range of values to obtain full current-voltage characteristics.

3. Preprocessor Flags
---------------------
Set preprocessor flags in the ``../Source/Code_Definitions.H`` file before compiling the code, depending on your configuration needs.

The important ones are: 

- ``#define NUM_MODES 1`` sets the size of block for each matrix element used in NEGF. 
  For example, for modeling carbon nanotubes with single mode using mode-space approximation, NUM_MODES is set to 1, which implies each element of Hamiltonian matrix is a number. If it were 2, it would be an array of size 2. For other materials, this number may set the matrix block as a submatrix of size ``NUM_MODES x NUM_MODES``.

- ``#define NUM_CONTACTS 2`` sets number of metal leads to 2 for source and drain. At present, the code is verified for 2 leads.